It would be helpful if we could represent our scene config in a declarative format, both for concision and because it opens the door to live updating the UI in the test app.
 

It would be helpful if we could represent our scene config in a format that permits trivial addition/modification of the scene -- ideally realtime updates and a format that is concise enough that it's possible to get a sense of the entire scene hierarchy by looking at the description.

A declarative format is a common approach for this.