In Superpowers Game, Scene editor, is there currently any way to make a customizable property which is a dropdown of named options, for example a list of acceptable strings or the possible values explicitly declared in an enum?
No. Only boolean, number. string, and Vector2/3 are valid customizable property types the UI can display. The rest get silently dropped with a debug console error you can't see unless you open your browser console. (Can that even be done in Superpowers App?)