This wouldn't be translating a button, it would be assigning a whole new "next-playlist" function which may or may not exist yet.
Correct.
However, in some cases, you can work around this limitation with the
Tweak Order feature.
For instance, if the reason you want to hit "Next Playlist" is because you're trying to skip to the next album in a sequential Artist/Album tree, then you can simply hold the 3 button on the Rio remote control and it will dump the current album and start playing the next one. This works for Artist and Genre, too.