Not sure if this was possible in prior versions to 26, at least I didn’t know how to do this: it is possible to create an empty playlist folder and using multi gestures it is possible to move one or several playlists in or out of said folder. In order to do this in the past I always needed to open up my MacBook and open the music app there to do so.
I have several playlists which I order in folders. Ordering was only possible on macOS but is now possible on iOS too.