I have used https://github.com/danieladov/jellyfin-plugin-mergeversions in the past and it merged movies from different paths (I forgot I already owned the movie in worse quality). But I have no experience with different drives.

I recently set up a bunch of these in my adguard home filter list. They do not only block ads, but also Fake-Shops, Cryptomining, Gambling and more shady stuff.

I don't like honest bookmarks as well. A proper bookmark should be mean-spirited and lie to me, so that I'll never find my place again!