The problem is that when you change cards, the files are no longer in the same place. Even if you use the same file organisation, afaik, android treats it as though it's separate because I've switched cards back and forth, with each card being recognized properly, but not interchangeably despite being an exact copy, having copy/pasted from one to the other.

It you use a file manager like mixplorer, you can see that each card gets a unique identifier. You pull one, slap the next in, and the identifier changes. You slap the first one back, and it gets its original number.

That being said, most music players create and read playlists from media storage. So import/export is easy enough as long as the player has an import option at all.

Poweramp is my player of choice, and it will import system playlists manually. Most of the rest do it by default. Iirc, gonemad and jet do. Been a few years since I checked out the other big ones, but I recall it being a normal thing.