James,
we are currently working on an article which explains the method for such value lists (would be too long for a forum post). Hang in there, please.
Here are some hints, so you can work it out for yourself if it’s urgent:
our labels use the ui_custom_popup_infield GDL command. It can create a “value list” using the returned array values of requests in the User Interface script alone. The selected value can be displayed in 2D.
Dominika Bobály
Library Developer, Library Team
GRAPHISOFT SE