Try to fix Edit Custom Fields button not working. Removed duplicate option from Boards Settings.

Thanks to xet7 !

Fixes #5988

client/components/sidebar/sidebar.jade

@@ -631,10 +631,10 @@ template(name="boardMenuPopup")
     if currentUser.isBoardAdmin
       hr
       ul.pop-over-list
-        li
-          a.js-delete-duplicate-lists
-            | 🗑️
-            | {{_ 'delete-duplicate-lists'}}
+        // li
+        //   a.js-delete-duplicate-lists
+        //     | 🗑️
+        //     | {{_ 'delete-duplicate-lists'}}
         li
           a.js-archive-board
             | ➡️📦

client/components/sidebar/sidebarCustomFields.jade

@@ -95,3 +95,7 @@ template(name="createCustomFieldPopup")
 template(name="deleteCustomFieldPopup")
     p {{_ "custom-field-delete-pop"}}
     button.js-confirm.negate.full(type="submit") {{_ 'delete'}}
+
+// Reuse the create form for editing to satisfy popup template lookup
+template(name="editCustomFieldPopup")
+    +Template.dynamic(template="createCustomFieldPopup")