I’ve just done some video using the size/position/rotation filter with keyframes for pinning a moving closeup (cf https://www.youtube.com/watch?v=3VXQQpLe1Lk ). I did the keyframes by skipping forward in the movie until the bellows direction reverses, then using the handle on the size/position/rotation filter to put the right side bar into correct position/orientation.
Here are some observations: the motion tracking filter doesn’t do rotations. Putting that aside, there did not seem any way to cut out its tracked area and put it in a constant position. Putting that aside, it totally did not work: the preview was pretty promising, but after analysis, everything was totally off, including the starting frame set manually for tracking. No idea what editing operation caused the track to not work with analysis or caused the analysis results to get interpreted wrongly. I suppose that someone will hunt this down, but as I said: there are other hurdles for applying the results of the motion tracker to my problem anyway.
Then with regard to righting my right side bar using the size/rotation handles: it was rather awkward that pulling on the handle only results in angles 0° to 359° because whenever the tilt was to the left, I had to manually subtract 360° in order not to get caprioles due to the keyframing.
So my suggestion would be that if keyframing is in effect, the handle does not disambiguate the angle’s 360° multiplicity by minimizing the difference to 180° but by minimizing the difference to the last keyframe’s rotation angle. In case this still isn’t right (or not implemented) two buttons for fixing up the angle by -360° or +360° would make this somewhat less annoying.
Even better would be to just maintain continuity when pulling the handle around and not let it jump by 360° when the user drags it across the 0° mark. Then one could add twirls manually.
I don’t have a good idea how to deal with the situation that might arise when you edit stuff at the start, making things upright, then edit stuff at the end, and then end up with a 360° mismatch in the middle. The +/-360° buttons may help straightening things up all the way to end, but it would still be a nuisance.
But usually editing will move from start to end instead of doing patchwork, so I am probably overthinking this.