diff --git a/CHANGELOG-WIP.md b/CHANGELOG-WIP.md
index bd6f45a76d6..1162d88fde5 100644
--- a/CHANGELOG-WIP.md
+++ b/CHANGELOG-WIP.md
@@ -448,6 +448,7 @@
 - `craft\helpers\StringHelper::toString()` now supports backed enums.
 - `craft\i18n\I18N::getPrimarySiteLocale()` is now deprecated. `craft\models\Site::getLocale()` should be used instead.
 - `craft\i18n\I18N::getPrimarySiteLocaleId()` is now deprecated. `craft\models\Site::$language` should be used instead.
+- `craft\models\FieldLayout::getField()` and `isFieldIncluded()` now now have a `$filter` argument rather than `$attribute`, and it can be set to a callable.
 - `craft\models\Section::$propagationMethod` now has a type of `craft\enums\PropagationMethod`.
 - `craft\services\AssetIndexer::indexFileByListing()` now has a `$volume` argument in place of `$volumeId`.
 - `craft\services\AssetIndexer::indexFolderByListing()` now has a `$volume` argument in place of `$volumeId`.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c0bf70a67db..f86921dfe64 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@
 - Added `craft\services\Relations::deleteLeftoverRelations()`. ([#13956](https://github.com/craftcms/cms/issues/13956))
 - Added `craft\services\Search::shouldCallSearchElements()`. ([#14293](https://github.com/craftcms/cms/issues/14293))
 - `craft\behaviors\SessionBehavior::setSuccess()` and `getSuccess()` use the `success` flash key now, rather than `notice`. ([#14345](https://github.com/craftcms/cms/pull/14345))
+- `craft\models\FieldLayout::getField()` and `isFieldIncluded()` now now have a `$filter` argument rather than `$attribute`, and it can be set to a callable.
 - Exception response data no longer includes an `error` key with the exception message. `message` should be used instead. ([#14346](https://github.com/craftcms/cms/pull/14346))
 - Relations for fields that are no longer included in an element’s field layout are now deleted after element save. ([#13956](https://github.com/craftcms/cms/issues/13956))
 - Assets fields’ selection modals now open to the last-viewed location by default, if their Default Upload Location doesn’t specify a subpath. ([#14382](https://github.com/craftcms/cms/pull/14382))
@@ -23,6 +24,7 @@
 - Fixed a bug where non-global custom fields were being shown on the Fields index page when searching. ([#14344](https://github.com/craftcms/cms/issues/14344))
 - Fixed a bug where component slideouts would open when long-pressing on a component’s action menu button or drag handle within a component select input.
 - Fixed various issues with Tags fields. ([#14356](https://github.com/craftcms/cms/issues/14356), [#14359](https://github.com/craftcms/cms/pull/14359))
+- Fixed a bug where it was possible to include single-instance fields multiple times in a field layout. ([#14352](https://github.com/craftcms/cms/issues/14352))
 - Fixed a bug where read/write splitting was always getting disabled for GraphQL POST requests. ([#14324](https://github.com/craftcms/cms/issues/14324))
 - Fixed a bug where GraphQL schema edit pages could include empty category headings.
 - Fixed a bug where asset slideouts weren’t showing validation errors on the Filename field. ([#14329](https://github.com/craftcms/cms/issues/14329))
diff --git a/src/helpers/Cp.php b/src/helpers/Cp.php
index 2f27c665b43..cc986771fc2 100644
--- a/src/helpers/Cp.php
+++ b/src/helpers/Cp.php
@@ -2533,9 +2533,17 @@ private static function _fldFieldSelectorsHtml(string $groupName, array $groupFi
 
     private static function _showFldFieldSelector(FieldLayout $fieldLayout, BaseField $field): bool
     {
+        $attribute = $field->attribute();
+        $uid = $field instanceof CustomField ? $field->getField()->uid : null;
+
         return (
             $field->isMultiInstance() ||
-            !$fieldLayout->isFieldIncluded($field->attribute())
+            !$fieldLayout->isFieldIncluded(function(BaseField $field) use ($attribute, $uid) {
+                if ($field instanceof CustomField) {
+                    return $field->getField()->uid === $uid;
+                }
+                return $field->attribute() === $attribute;
+            })
         );
     }
 
diff --git a/src/models/FieldLayout.php b/src/models/FieldLayout.php
index 81dc66da35a..faa4ce5323d 100644
--- a/src/models/FieldLayout.php
+++ b/src/models/FieldLayout.php
@@ -470,16 +470,16 @@ public function getAvailableUiElements(): array
     }
 
     /**
-     * Returns whether a field is included in the layout by its attribute.
+     * Returns whether a field is included in the layout by a callback or its attribute
      *
-     * @param string $attribute
+     * @param callable|string $filter
      * @return bool
      * @since 3.5.0
      */
-    public function isFieldIncluded(string $attribute): bool
+    public function isFieldIncluded(callable|string $filter): bool
     {
         try {
-            $this->getField($attribute);
+            $this->getField($filter);
             return true;
         } catch (InvalidArgumentException) {
             return false;
@@ -487,24 +487,30 @@ public function isFieldIncluded(string $attribute): bool
     }
 
     /**
-     * Returns a field that’s included in the layout by its attribute.
+     * Returns a field that’s included in the layout by a callback or its attribute name.
      *
-     * @param string $attribute
+     * @param callable|string $filter
      * @return BaseField
      * @throws InvalidArgumentException if the field isn’t included
      * @since 3.5.0
      */
-    public function getField(string $attribute): BaseField
+    public function getField(callable|string $filter): BaseField
     {
-        $filter = fn(FieldLayoutElement $layoutElement) => (
-            $layoutElement instanceof BaseField &&
-            $layoutElement->attribute() === $attribute
-        );
+        if (is_string($filter)) {
+            $attribute = $filter;
+            $filter = fn(BaseField $field) => $field->attribute() === $attribute;
+        }
+
         /** @var BaseField|null $field */
-        $field = $this->_element($filter);
+        $field = $this->_element(fn(FieldLayoutElement $layoutElement) => (
+            $layoutElement instanceof BaseField &&
+            $filter($layoutElement)
+        ));
+
         if (!$field) {
-            throw new InvalidArgumentException("Invalid field: $attribute");
+            throw new InvalidArgumentException(isset($attribute) ? "Invalid field: $attribute" : 'Invalid field');
         }
+
         return $field;
     }