Kudo's Herbert, and I am looking forward to the Attribute Setter widget. And I did notice that you also use the trick to put two reference selectors close together (the input and the standard Mendix widget so you only see the select form button). Would be nice if the input reference selector could have the button with the popup form incorporated.
Check out the widget in the appstore: https://appstore.home.mendix.com/link/app/2029/Appronto/UXManipulator
Attribute Setter widget == UX Manipulator widget :)