Track monitoring switch separate to track output
Premiere has a mechanism for viewing the output in program/record monitor of different video track outputs. Premiere's mechanism works like photoshop's layer output toggles, there's an eyeball icon for each track to toggle it's output on and off, and you can even kinda 'solo' them too by disabling all tracks with shift+click and then enabling the one you want.
This is inconvenient when you want to temporarily monitor tracks that lower are down in the stack because it requires the disabling of multiple tracks above the one you want, and also re-enabling of all those tracks thereafter. The current system is still very good when you want that granular control of per-track visibility and should remain in place, however often when you are editing what you really want is not so much individual track output toggles so much as a 'track monitoring' switch to adjust how far up the stack of tracks you'd like see in the program monitor's output. With that system you could for example in an 8 video track-high timeline, select track 5 for monitoring whilst leaving tracks 1-4 untouched and do it in just one click/keystroke instead of 3. This is important because not only do you save on having to both disable and re-enable to tracks above track 5 if you only temporarily wanted to monitor that track, but also, because there are often stacked effects that work with transparency and composite modes underneath the track you want to monitor and you want those to remain on, which is another thing that makes this track monitoring suggestions separate to a solo track output toggle which would show ONLY the output of track 6 and not any tracks below it whose output is blended through transparency with track 6. Used in conjunction with the existing track output system this would provide ideal monitoring control because you could adjust stack-monitoring position first and then toggle individual tracks within that stack if needed.