I think you might be right right
Few months ago when I bought my new desktop PC I thought that my problem [on desktop] was largely gone as most of the time Mp3tag did retaineposition of my Filter box between sessions. But then some day I finally noticed that it no longer merely sometimes [which was good enough for me] but always was not in the place it was left when I closed Mp3tag the last time. So my problem was back with full force. Between that observation and the day I installed Windows I did perform at least one update - so maybe it was it this that caused the bug to return in its whole glory
So today I kind of repeated this experiment
as I have now a new desktop machine and still that old laptop but with newer operating system. In both cases the system is Windows 10 installed from scratch - but the laptop has an older version. And on both systems I have successfully blocked updates [using Windows Update Blocker]
[Previously the experiment was performed on Windows 7]
Results came down to this: my old Mp3tag settings put on laptop were A-OK and all new default settings [after installations of Mp3tag] were A-OK on both desktop and laptop. But the very old settings that work properly on laptop [which have older Windows 10] on desktop [which has a newer version of Windows] run with that bug of mine
All in all after some additional tests I:
1] removed Mp3tag from desktop
2] installed Mp3tag 3.08
3] copied by hand options available under File > Options by simply selecting on desktop what I saw on laptop
4] copied all of old config files to my new installation - except mp3tag.cfg file
And now finally after all those years it seems that my Filter box finally understands that it is suppose to stay in the same place after closing of the Mp3tag
But I fear that with time it will start acting faulty once again- after some update of Windows and / or Mp3tag. And yes: My multiple action were messed after step 4 as they meticulous placement on the list was replaced with default alphabetical sort order. So if my bug comes back I will not indulge myself again in repeating of this tedious task