Hi @bjoerka,
This issue is handled with the new Task Overview "T02119-Data Manager v2.0" for Vectorworks 2023. There will be new Custom Property Sets Manager where you can define the field as Popup and set its values. The Custom Property Sets will no longer rely on Records and the user will have the ability to create Property Set without the need of a Record.
In the currently released version it is not possible to define the Custom Property Set's field as Popup.
Regards,
Nick