Identifying files in directory that are NOT being seeded

[kingqueen]

I have 849 torrents seeding in qBittorrent. As a result, in my seeding directory I have 3Tb of files - 11,540 files in 880 directories. (Actually in subdirectories etc.)
Some of them have been seeding for over 5 years (transferred from uTorrent).
I would like a way of finding out which of these files and directories are NOT part of torrents being seeded by qBittorrent.
Is there a way to do this, please?
Thank you

[Switeck]

I don't know any way to do so, short of telling qBT to move or delete all the torrents it has loaded...which tends to be most undesirable to do!

[kingqueen]

I like that lateral thinking, thank you!
Actually I think that may be doable. The move, anyway. Particularly as if moving within a disk, it doesn't actually thrash the disk.

[MountainInside]

I would backup qBittorrent data files and the 3TB folder to different drive first, delete all the files from qB and then I'll be left out with folders that aren't used by qB, now I can compare with the backed up 3TB folder and delete the files from the backup folder, finally I'll restore the original qB data files and folder to their original locations.