[DOCS] Add hint regarding combined identifier usage

Resolves: #108300
Related: #107683
Releases: main
Change-Id: I0f2bc41cd64a316b468147fc28bfcf50e9dd3153
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/91886
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Garvin Hicking <garvin@hick.ing>
Tested-by: Oli Bartsch <bo@cedev.de>
Tested-by: Garvin Hicking <garvin@hick.ing>
Reviewed-by: Josua Vogel <j.vogel97@web.de>
Tested-by: Josua Vogel <j.vogel97@web.de>
Reviewed-by: Oli Bartsch <bo@cedev.de>

Author: o-ba

typo3/sysext/core/Documentation/Changelog/14.0/Feature-107683-FileStorageTreeItemsModificationEventAndLabelSupport.rst

@@ -27,11 +27,16 @@ TSconfig, using the combined identifier of the folder:
 ..  code-block:: typoscript
     :caption: EXT:my_extension/Configuration/user.tsconfig
 
-    options.folderTree.label.1:/campaigns {
+    options.folderTree.label.1:/campaigns/ {
         label = Main Storage
         color = #ff8700
     }
 
+..  important::
+
+    Make sure to always use the full identifier, which also contains a
+    trailing slash (`/`).
+
 Labels and status information
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