I'd argue that this concept for media is most commonly known as "playlists" and unfortunately only used within data silos, e.g. a playlist of YouTube videos, a Spotify playlist, a TV season of episodes, a series of episodes, a trilogy, etc.
(Yes, I'd argue that your music library of mp3 files is also kind of a silo, although portable)
Heck, even a slideshow is arguably a playlist.
I agree that putting a playlist-like concept into, say, the filesystem would be an extremely interesting idea but I think a big danger is running into the same problem as hardlinks and symlinks.
This problem is that if a file is "present" in multiple places (or playlists) deleting/modifying/moving it can have unforeseen consequences and it's hard to reason about (and if you copy the file now you get to invent a way to track different versions too!).
I think this is also holding tagging filesystems back.
I'm currently writing a non-hierarchical FUSE filesystem and have been thinking about this list-directory concept but I'm still not completely sure how it would work, especially since I need to remain backwards compatible with the POSIX interfaces.
Will probably have to just try it out (xattrs to the rescue?) and see what sticks I suppose...
I first read about it via this blog post: https://shkspr.mobi/blog/2019/04/banish-the-%ef%bf%bd-with-u...