I have always been wishing for a quick and simple way to have a complete overview of the contents of all tags for a track.
For that purpose I created this 'Tag Info' theater mode. (embedded)
It is not an interactive Theater Mode, and it has no controls you can interact with.
It's a static screen displaying most of the available tagging information for a track, including how it's custom and virtual tags are being populated.
I'm not satisfied with the workings of this creation and have retracted it.