diff --git a/backend/src/baserow/contrib/integrations/local_baserow/service_types.py b/backend/src/baserow/contrib/integrations/local_baserow/service_types.py
index a0d0fe8522..ee6b1bb43c 100644
--- a/backend/src/baserow/contrib/integrations/local_baserow/service_types.py
+++ b/backend/src/baserow/contrib/integrations/local_baserow/service_types.py
@@ -2327,12 +2327,12 @@ def get_data():
                 local_model, RowSerializer, is_response=True, user_field_names=True
             )
 
-            return {
+            data_to_process = {
                 "results": serializer(rows, many=True).data,
                 "has_next_page": False,
             }
 
-        data_to_process = self._prepare_result(table.get_model(), data_to_process)
+            return self._prepare_result(local_model, data_to_process)
 
         self._process_event(
             self.model_class.objects.filter(table=table),
diff --git a/backend/src/baserow/core/populate.py b/backend/src/baserow/core/populate.py
index 00e878cf4f..c26eb2f339 100644
--- a/backend/src/baserow/core/populate.py
+++ b/backend/src/baserow/core/populate.py
@@ -14,6 +14,11 @@ def load_test_data():
     print("Add basic users...")
     user_handler = UserHandler()
 
+    # Allow to import any external archive
+    core_settings = CoreHandler().get_settings()
+    core_settings.verify_import_signature = False
+    core_settings.save()
+
     for i in range(3):
         # Create main admin
         email = f"admin{i + 1}@baserow.io" if i > 0 else "admin@baserow.io"
diff --git a/changelog/entries/unreleased/bug/improve_performances_when_editing_a_createupdate_workflow_ac.json b/changelog/entries/unreleased/bug/improve_performances_when_editing_a_createupdate_workflow_ac.json
new file mode 100644
index 0000000000..d56a87ca50
--- /dev/null
+++ b/changelog/entries/unreleased/bug/improve_performances_when_editing_a_createupdate_workflow_ac.json
@@ -0,0 +1,9 @@
+{
+    "type": "bug",
+    "message": "Improve performances when editing a create/update workflow action with a lot of table fields",
+    "issue_origin": "github",
+    "issue_number": null,
+    "domain": "builder",
+    "bullet_points": [],
+    "created_at": "2025-11-20"
+}
\ No newline at end of file
diff --git a/changelog/entries/unreleased/feature/allow_the_local_baserow_update_row_service_to_update_data_sy.json b/changelog/entries/unreleased/feature/allow_the_local_baserow_update_row_service_to_update_data_sy.json
new file mode 100644
index 0000000000..956e208668
--- /dev/null
+++ b/changelog/entries/unreleased/feature/allow_the_local_baserow_update_row_service_to_update_data_sy.json
@@ -0,0 +1,9 @@
+{
+    "type": "feature",
+    "message": "Allow the Local Baserow 'update row' service to update data synced tables with writable fields.",
+    "issue_origin": "github",
+    "issue_number": 3799,
+    "domain": "integration",
+    "bullet_points": [],
+    "created_at": "2025-11-19"
+}
diff --git a/web-frontend/modules/builder/locales/en.json b/web-frontend/modules/builder/locales/en.json
index 9f8e454958..731a39707d 100644
--- a/web-frontend/modules/builder/locales/en.json
+++ b/web-frontend/modules/builder/locales/en.json
@@ -908,15 +908,6 @@
     "dataSource": "Data source",
     "formulas": "Formulas"
   },
-  "localBaserowServiceForm": {
-    "integrationDropdownLabel": "Integration",
-    "rowIdLabel": "Row ID",
-    "rowIdPlaceholder": "Select a row ID"
-  },
-  "upsertRowWorkflowActionForm": {
-    "fieldMappingPlaceholder": "Choose a field value",
-    "noTableSelectedMessage": "Choose a table to begin configuring your fields."
-  },
   "fieldMappingContext": {
     "enableField": "Enable field",
     "disableField": "Disable field"
diff --git a/web-frontend/modules/core/assets/scss/components/integrations/local_baserow/local_baserow_form.scss b/web-frontend/modules/core/assets/scss/components/integrations/local_baserow/local_baserow_form.scss
index 8b1dd3d510..3f2aa63b50 100644
--- a/web-frontend/modules/core/assets/scss/components/integrations/local_baserow/local_baserow_form.scss
+++ b/web-frontend/modules/core/assets/scss/components/integrations/local_baserow/local_baserow_form.scss
@@ -8,3 +8,11 @@
     flex: 1 0 auto;
   }
 }
+
+.field-mapping-form__placeholder {
+  width: 100%;
+  height: 36px;
+  background-color: $white;
+
+  @include rounded($rounded-md);
+}
diff --git a/web-frontend/modules/core/components/InViewport.vue b/web-frontend/modules/core/components/InViewport.vue
new file mode 100644
index 0000000000..e9a88c60d9
--- /dev/null
+++ b/web-frontend/modules/core/components/InViewport.vue
@@ -0,0 +1,32 @@
+<template>
+  <div ref="rootEl">
+    <template v-if="isVisible">
+      <slot />
+    </template>
+    <template v-else><slot name="placeholder">...</slot></template>
+  </div>
+</template>
+
+<script setup>
+import { ref, onMounted, onBeforeUnmount } from 'vue'
+
+const isVisible = ref(false)
+const rootEl = ref(null)
+let observer = null
+
+onMounted(() => {
+  observer = new IntersectionObserver(
+    (entries) => {
+      // Update visibility based on intersection
+      if (entries[0].isIntersecting) isVisible.value = true
+    },
+    { threshold: 0.1 }
+  )
+
+  if (rootEl.value) observer.observe(rootEl.value)
+})
+
+onBeforeUnmount(() => {
+  if (observer && rootEl.value) observer.unobserve(rootEl.value)
+})
+</script>
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/FieldMapping.vue b/web-frontend/modules/integrations/localBaserow/components/services/FieldMapping.vue
deleted file mode 100644
index 442a793528..0000000000
--- a/web-frontend/modules/integrations/localBaserow/components/services/FieldMapping.vue
+++ /dev/null
@@ -1,32 +0,0 @@
-<template>
-  <InjectedFormulaInput
-    v-model="fieldValue"
-    :disabled="!fieldMapping.enabled"
-    v-bind="$attrs"
-  />
-</template>
-
-<script>
-import InjectedFormulaInput from '@baserow/modules/core/components/formula/InjectedFormulaInput'
-
-export default {
-  name: 'FieldMapping',
-  components: { InjectedFormulaInput },
-  props: {
-    fieldMapping: {
-      type: Object,
-      required: true,
-    },
-  },
-  computed: {
-    fieldValue: {
-      get() {
-        return this.fieldMapping.value
-      },
-      set(value) {
-        this.$emit('change', { value })
-      },
-    },
-  },
-}
-</script>
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingContext.vue b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingContext.vue
index d503dfb620..09e3da9e2b 100644
--- a/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingContext.vue
+++ b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingContext.vue
@@ -2,12 +2,7 @@
   <Context :overflow-scroll="true" :max-height-if-outside-viewport="true">
     <ul class="context__menu">
       <li class="context__menu-item">
-        <a
-          class="context__menu-item-link"
-          @click.prevent="
-            handleEditClick({ enabled: !fieldMapping.enabled, value: '' })
-          "
-        >
+        <a class="context__menu-item-link" @click.prevent="handleEditClick()">
           <i class="context__menu-item-icon" :class="enabledClass"></i>
           {{ toggleEnabledText }}
         </a>
@@ -39,8 +34,11 @@ export default {
     },
   },
   methods: {
-    handleEditClick(change) {
-      this.$emit('edit', change)
+    handleEditClick() {
+      this.$emit(
+        'edit',
+        this.fieldMapping.enabled ? undefined : { enabled: true, formula: '' }
+      )
       this.hide()
     },
   },
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingForm.vue b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingForm.vue
index a97eeb06d8..eb4b9489ed 100644
--- a/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingForm.vue
+++ b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingForm.vue
@@ -1,116 +1,107 @@
 <template>
-  <div>
-    <FormGroup
-      v-for="field in filteredFields"
-      :key="field.id"
-      small-label
-      :label="field.name"
-      required
-      class="margin-bottom-2"
-    >
-      <FieldMapping
-        :field-mapping="field.mapping"
-        :placeholder="$t('upsertRowWorkflowActionForm.fieldMappingPlaceholder')"
-        @change="updateFieldMapping(field.id, $event)"
-      />
+  <div v-if="mapping?.enabled">
+    <FormGroup small-label :label="field.name" required class="margin-bottom-2">
+      <InViewport>
+        <InjectedFormulaInput
+          :key="`${field.id} ${mapping.enabled}`"
+          v-model="fieldValue"
+          :disabled="!mapping.enabled"
+          :placeholder="
+            $t('upsertRowWorkflowActionForm.fieldMappingPlaceholder')
+          "
+        />
+        <template #placeholder>
+          <div class="field-mapping-form__placeholder" />
+        </template>
+      </InViewport>
       <template #after-input>
-        <div :ref="`editFieldMappingOpener-${field.id}`">
+        <div :ref="`editFieldMappingOpener`">
           <ButtonIcon
             type="secondary"
             icon="iconoir-more-vert"
-            @click="openContext(field)"
+            @click="openContext()"
           />
         </div>
         <FieldMappingContext
-          :ref="`fieldMappingContext-${field.id}`"
-          :field-mapping="field.mapping"
-          @edit="updateFieldMapping(field.id, $event)"
+          :ref="`fieldMappingContext`"
+          :field-mapping="mapping"
+          @edit="$emit('update', $event)"
         />
       </template>
     </FormGroup>
   </div>
+  <div v-else>
+    <FormGroup small-label :label="field.name" required class="margin-bottom-2">
+      <Button type="secondary" @click="$emit('update', defaultEmptyFormula())">
+        {{ $t('fieldMappingContext.enableField') }}
+      </Button>
+    </FormGroup>
+  </div>
 </template>
 
 <script>
-import FieldMapping from '@baserow/modules/integrations/localBaserow/components/services/FieldMapping'
 import FieldMappingContext from '@baserow/modules/integrations/localBaserow/components/services/FieldMappingContext'
+import InjectedFormulaInput from '@baserow/modules/core/components/formula/InjectedFormulaInput'
+import InViewport from '@baserow/modules/core/components/InViewport'
 
 export default {
   name: 'FieldMappingForm',
-  components: { FieldMappingContext, FieldMapping },
+  components: { FieldMappingContext, InjectedFormulaInput, InViewport },
   inject: ['workspace'],
   props: {
-    value: {
-      type: Array,
+    field: {
+      type: Object,
       required: true,
     },
-    fields: {
-      type: Array,
-      required: true,
+    mapping: {
+      type: Object,
+      required: false,
+      default: undefined,
     },
   },
+  data() {
+    return {
+      localValue: this.mapping?.value,
+      debounceTimeout: null,
+    }
+  },
   computed: {
-    filteredFields() {
-      return this.fields
-        .map((field) => ({
-          ...field,
-          mapping: this.getFieldMapping(field.id),
-        }))
-        .filter((field) => this.canWriteFieldValues(field))
+    fieldValue: {
+      get() {
+        return this.localValue
+      },
+      set(value) {
+        this.localValue = value
+
+        // Debouncing value update as it produces performance issues when they are
+        // a lot of fields
+        clearTimeout(this.debounceTimeout)
+        this.debounceTimeout = setTimeout(() => {
+          this.$emit('update', { value })
+        }, 500)
+      },
+    },
+  },
+  watch: {
+    'mapping.value'(newValue) {
+      this.localValue = newValue
     },
   },
   methods: {
-    openContext(field) {
-      this.$refs[`fieldMappingContext-${field.id}`][0].toggle(
-        this.$refs[`editFieldMappingOpener-${field.id}`][0],
+    defaultEmptyFormula() {
+      return {
+        enabled: true,
+        value: { formula: '""' },
+      }
+    },
+    openContext() {
+      this.$refs.fieldMappingContext.toggle(
+        this.$refs.editFieldMappingOpener,
         'bottom',
         'left',
         4
       )
     },
-    canWriteFieldValues(field) {
-      return this.$hasPermission(
-        'database.table.field.write_values',
-        field,
-        this.workspace.id
-      )
-    },
-    getFieldMapping(fieldId) {
-      return (
-        this.value.find(
-          (fieldMapping) => fieldMapping.field_id === fieldId
-        ) || { enabled: true, field_id: fieldId, value: {} }
-      )
-    },
-    updateFieldMapping(fieldId, changes) {
-      const existingMapping = this.value.some(
-        ({ field_id: existingId }) => existingId === fieldId
-      )
-      const existingFieldIds = this.fields.map(({ id }) => id)
-
-      // If the field has been removed in the meantime we want to ignore it
-      const filteredValue = this.value.filter(({ field_id: fieldId }) =>
-        existingFieldIds.includes(fieldId)
-      )
-
-      if (existingMapping) {
-        const newMapping = filteredValue.map((fieldMapping) => {
-          if (fieldMapping.field_id === fieldId) {
-            return { ...fieldMapping, ...changes }
-          }
-          return fieldMapping
-        })
-        this.$emit('input', newMapping)
-      } else {
-        const newMapping = filteredValue
-        newMapping.push({
-          enabled: true,
-          field_id: fieldId,
-          ...changes,
-        })
-        this.$emit('input', newMapping)
-      }
-    },
   },
 }
 </script>
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingsForm.vue b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingsForm.vue
new file mode 100644
index 0000000000..0f9ce81f83
--- /dev/null
+++ b/web-frontend/modules/integrations/localBaserow/components/services/FieldMappingsForm.vue
@@ -0,0 +1,91 @@
+<template>
+  <div>
+    <FieldMappingForm
+      v-for="field in filteredFields"
+      :key="field.id"
+      :field="field"
+      :mapping="fieldMappingMap[field.id]"
+      @update="updateFieldMapping(field.id, $event)"
+    />
+  </div>
+</template>
+
+<script>
+import FieldMappingForm from '@baserow/modules/integrations/localBaserow/components/services/FieldMappingForm'
+
+export default {
+  name: 'FieldMappingsForm',
+  components: { FieldMappingForm },
+  inject: ['workspace'],
+  props: {
+    value: {
+      type: Array,
+      required: true,
+    },
+    fields: {
+      type: Array,
+      required: true,
+    },
+  },
+  computed: {
+    fieldMappingMap() {
+      return Object.fromEntries(
+        this.value.map((fieldMapping) => [fieldMapping.field_id, fieldMapping])
+      )
+    },
+    filteredFields() {
+      return this.fields.filter((field) => this.canWriteFieldValues(field))
+    },
+  },
+  methods: {
+    canWriteFieldValues(field) {
+      return this.$hasPermission(
+        'database.table.field.write_values',
+        field,
+        this.workspace.id
+      )
+    },
+    updateFieldMapping(fieldId, changes) {
+      const existingMapping = this.value.some(
+        ({ field_id: existingId }) => existingId === fieldId
+      )
+      const existingFieldIds = this.fields.map(({ id }) => id)
+
+      // If the field has been removed in the meantime we want to ignore it
+      const filteredValue = this.value.filter(({ field_id: fieldId }) =>
+        existingFieldIds.includes(fieldId)
+      )
+
+      if (existingMapping) {
+        if (changes === undefined) {
+          this.$emit(
+            'input',
+            filteredValue.filter(
+              ({ field_id: fieldIdToCheck }) => fieldIdToCheck !== fieldId
+            )
+          )
+        } else {
+          this.$emit(
+            'input',
+            filteredValue.map((fieldMapping) => {
+              if (fieldMapping.field_id === fieldId) {
+                return { ...fieldMapping, ...changes }
+              }
+              return fieldMapping
+            })
+          )
+        }
+      } else if (changes !== undefined) {
+        this.$emit('input', [
+          ...filteredValue,
+          {
+            enabled: true,
+            field_id: fieldId,
+            ...changes,
+          },
+        ])
+      }
+    },
+  },
+}
+</script>
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowServiceForm.vue b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowServiceForm.vue
index 47a14bbade..820d7626cc 100644
--- a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowServiceForm.vue
+++ b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowServiceForm.vue
@@ -91,7 +91,7 @@ export default {
     },
     /**
      * Whether to disallow the selection of data synced tables. Data sources
-     * can select them, but workflow actions cannot.
+     * can select them, but a create-row workflow action cannot.
      */
     disallowDataSyncedTables: {
       type: Boolean,
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpdateRowServiceForm.vue b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpdateRowServiceForm.vue
index 569ba3b65c..55bb7f6a15 100644
--- a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpdateRowServiceForm.vue
+++ b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpdateRowServiceForm.vue
@@ -1,6 +1,7 @@
 <template>
   <UpsertRowWorkflowActionForm
     enable-row-id
+    :disallow-data-synced-tables="false"
     v-bind="$attrs"
     v-on="$listeners"
   />
diff --git a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpsertRowServiceForm.vue b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpsertRowServiceForm.vue
index f128549732..56edeb5765 100644
--- a/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpsertRowServiceForm.vue
+++ b/web-frontend/modules/integrations/localBaserow/components/services/LocalBaserowUpsertRowServiceForm.vue
@@ -5,25 +5,31 @@
       :application="application"
       :enable-view-picker="false"
       :default-values="defaultValues"
-      disallow-data-synced-tables
+      :disallow-data-synced-tables="disallowDataSyncedTables"
       @table-changed="handleTableChange"
       @values-changed="emitServiceChange($event)"
     ></LocalBaserowServiceForm>
     <div v-if="tableLoading" class="loading-spinner margin-bottom-1"></div>
     <p v-if="values.integration_id && !values.table_id">
-      {{ $t('upsertRowWorkflowActionForm.noTableSelectedMessage') }}
+      {{ $t('localBaserowUpsertRowServiceForm.noTableSelectedMessage') }}
     </p>
-    <FieldMappingForm
+    <FieldMappingsForm
       v-if="!tableLoading"
       v-model="values.field_mappings"
-      :fields="getWritableSchemaFields"
-    ></FieldMappingForm>
+      :fields="writableSchemaFields"
+    ></FieldMappingsForm>
+    <Alert
+      v-if="!tableLoading && service?.table_id && !writableSchemaFields.length"
+      type="warning"
+    >
+      <p>{{ $t('localBaserowUpsertRowServiceForm.noWritableFields') }}</p>
+    </Alert>
   </form>
 </template>
 
 <script>
 import _ from 'lodash'
-import FieldMappingForm from '@baserow/modules/integrations/localBaserow/components/services/FieldMappingForm'
+import FieldMappingsForm from '@baserow/modules/integrations/localBaserow/components/services/FieldMappingsForm'
 import form from '@baserow/modules/core/mixins/form'
 import LocalBaserowServiceForm from '@baserow/modules/integrations/localBaserow/components/services/LocalBaserowServiceForm'
 
@@ -31,7 +37,7 @@ export default {
   name: 'LocalBaserowUpsertRowServiceForm',
   components: {
     LocalBaserowServiceForm,
-    FieldMappingForm,
+    FieldMappingsForm,
   },
   mixins: [form],
   props: {
@@ -58,6 +64,17 @@ export default {
       required: false,
       default: false,
     },
+    /**
+     * Whether to disallow selecting data synced tables. It defaults to
+     * true as this is the default behaviour for the create row action
+     * form. The update row action form allows data synced tables, assuming
+     * they have writable fields.
+     */
+    disallowDataSyncedTables: {
+      type: Boolean,
+      required: false,
+      default: true,
+    },
   },
   data() {
     return {
@@ -75,7 +92,7 @@ export default {
      * Returns the writable fields in the schema, which the
      * `FieldMappingForm` can use to display the field mapping options.
      */
-    getWritableSchemaFields() {
+    writableSchemaFields() {
       if (
         this.service == null ||
         this.service.schema == null // have service, no table
diff --git a/web-frontend/modules/integrations/locales/en.json b/web-frontend/modules/integrations/locales/en.json
index 7fef2b9fe7..df37806f59 100644
--- a/web-frontend/modules/integrations/locales/en.json
+++ b/web-frontend/modules/integrations/locales/en.json
@@ -309,5 +309,15 @@
     "monthHelper": "This workflow will run every month on the specified day and time in your local timezone ({timezone})",
     "deactivatedTitle": "Periodic trigger deactivated",
     "deactivatedText": "This periodic trigger has been automatically deactivated due to consecutive failures."
+  },
+  "localBaserowServiceForm": {
+    "integrationDropdownLabel": "Integration",
+    "rowIdLabel": "Row ID",
+    "rowIdPlaceholder": "Select a row ID"
+  },
+  "localBaserowUpsertRowServiceForm": {
+    "fieldMappingPlaceholder": "Choose a field value",
+    "noTableSelectedMessage": "Choose a table to begin configuring your fields.",
+    "noWritableFields": "This table does not contain any writable fields."
   }
 }