Can't add/move "attribute" to the "User Search Lookup Attribute in IDM 4.8.1 AE

Hi

If I under Settings -> Customization -> User Search Lookup Attribute tries to drag a "Attbitubes"  from the Right Windows to the "User Search Lookup Attribute" is not possible.

The "Attribute" is created in the DAL -> Entities -> User (See screendump = DAL.JPG)

 

Best regards

Michael