Official comment
@Max > I'll address things through your post as you wrote them..
1) Even Serato DJ doesn't have a function to sort crates, you must be thinking of histories?
You can manually sort the playlists in rekordbox to have them in any order.
2) If you want to re-order the tracks, follow this example. Here is a sample playlist, sorted by play order, ascending - note that I've also set it so the tracks are in alphabetical order to match the numbered order:

Click the column header of the # column to reverse sort:

Next, click Playlist > Renumber Track Order and the play order will now change for the tracks:

Note that the numbered order is ascending, but the alphabetization is now reversed, showing that the list has effectively been inverted.

If you want to have the newest tracks at the top, you could do this with date added.