Hey @matthewh, and welcome to the community! You’re definitely correct - I just ran into this exact issue last week (we wanted to populate a table dropdown with a compound primary key that came from a different query). Right now, the table dropdown is indeed limited in scope to that particular row, or hardcoded values. This definitely shouldn’t be the case and we’ll see what we can do to fix it!
I’m hitting this as well. The ability to set the list of possible values in the drop-down based on another query, is kind of vital. Even if its only set for the entire table globally.