As far as I now it is not possible to revert back to previous versions of iOS. I doubt though that iOS 15.8.3 is the cause of your problem.
Where (how) are you trying to make these changes, on the iPod itself, in iTunes, the Apple Music app (on your PC) or in Finder? Bear in mind that even if it's possible to create a new playlist on the iPod from iTunes, that isn't the best way to do it. Instead, create or modify the playlist in iTunes and then add it to the iPod (and the simplest way is to use Sync).
You should also be able to create a playlist on your iPod and then Sync will add it to your iTunes library when the next sync is performed.