There’s a limit to what Prompts can do when they must be created once and then displayed. Any chance we could get callbacks when the user edits values, like GUI controls generally? i.e. when a select/list has its value changed, when a text field’s contents are modified, etc.
I have a different plan long term for more complex UI building, but what’s your specific use case? Validation? Manipulating the other controls in the prompt?
Any or all of the above! Really your lowest-cost/highest-flexibility option would be to go with the Keyboard Maestro option and allow presenting full HTML/CSS/JS popovers, with the ability to pass some kind of result back into the chain of action steps.