I use smart playlists a lot, but the fact that it is possible to sort them with only one sorting criterion is very limiting. If I sort them by album title the track numbers are messy, and so too if I sort them by rating or date.

It would be very useful to be able to sort them by multiple different sorting criteria, for example:

{
  year: ascending,
  rating: descending,
  album_title: ascending,
  tracks: ascending
}

ie: sort by year; then, in case of equal dates, sort them by rating, etc.

I hope you find my proposal interesting.