it seems that, in one way or another, I often lose my list of midi tracks in the piano roll. It would be nice if there were some sort of sub-screensets in the piano roll that would allow me to quickly save and recall a bunch of midi tracks in there instead of having to Pick Tracks all over again.

How about using the "Lock Contents" option (which appears by right-clicking on the MultiDock tab) to create multiple PRVs (in a single Screenset) displaying different sets of tracks?

wow I had never noticed that function before. no more double clicking a midi track and losing my old piano roll! awesome!