I think the method of documenting the entire framework through an all-encompassing demo is genius.
To this end, it might be an idea to demonstrate persisting data via ApplicationProperties.
That's the only thing I've needed so far that I wasn't able to find in the demo. I found it in the book.
Can't see any obvious place to put it tho...
Maybe a circle that you can reposition & change the colour of. Or some text. Maybe the audio settings tab is close enough? Or maybe it could just remember which tab was previously open. Although that would be quite easy to miss. Maybe a new tab?!