Two instances - a new workaround approach proposition

For the longest time there have been discussions on this forum about the inability of running more of Mp3tag than just one. But if I am not mistaken, something like this has not yet been proposed:

How about making within the Mp3tag room for more "instances"? The trick would be to have the ability to create additional main windows / list of files - and the ability to switch easily between them. Something like tabs in file managers. That would of course imply a possible work on the same files in different windows, thus a possibility for some kind of chaos to appear during the workflow, but that could be either somehow locked, marked or leftentirely to the discretion of the user

It would be also debatable, of the Filter box should remain one and the same or if every new window [tab] would get it its own. Or if it should be the user who would decide in what mode to operate; and in doing so, if the Filter box should get literally another box or utilize one and the same on-screen element for every "instance"

I would say that it does not matter whether the user interface shows several separate windows or one main window with several internal windows or tabs.
THis looks a lot like a diskussion on implementation principles and that would be completely off-topic and will lead us nowhere.
If you need more information, see good ole wikipedia for a start:

The principal problems have been discussed in depth.