I recognize this 'problem'. Many a time, I was puzzled: why do the tracks of a playlist show up, why not?
The good news is: this 'functionality' hasn't disappeared.
The 'bad' news is: you'll have to 'experiment' a bit... (coz it's unclear to me how to intentionally reproduce the problem)
So, for instance: (restart), create a new tab, click on 'Music' in Navigator, click on a playlist...
Hope you can work it out...
PS: I might have misinterpreted your problem (in function of my own experience). Maybe you mean that the playlists do not show up anymore in the playlist folder? Of course, that's another issue. (Normally, an update doesn't affect your playlists.)
Please, be more specific.