A "Where used" Feature for Tracks

I had a whole Folder with FLAC Files, from a Friend a few years Back. Many of those went in to Playlists i played semi regularly.
Now i encountered a CDJ900 setup where FLAC dont work, so i converted them all to MP3 320 Files.

Obviously the FLAC Files are missing, and i have to Relocate them. Since the Relocate OpenFile Dialog filters on File extension, this is not possible.

Im aware that Cue Points and/or grid analyise and all that would have to be re-done, whicht would be fine.

So i now have to leave in the Missing Files in my library, and when i go to a playlist, and encounte the [!] Symbol, i look this file up by name, to play it.

So when i remove a Track, it would be really Helpfull to know in which playlist it is still in use, otherwise all my playlists will lose some tracks that i converted and removed. 
I have no way to tell which tracks from which playlists get removed, so i just let them in there.

A feature to find where my tracks are used would really helpfull!
Like as a Filter the Sub-Explorer Window.

Bonus: if it would also show the Historie-Playlists filtered, it would be a super easy way to find which tracks i allready played after/before that one, which could be a very welcomed improvement when looking for the next track to play ;)