YouTube have decided to disable the API that makes this feature work.
YouTube does allow you to sort the Watch Later playlist by Date Added, Date Published and Popularity.
If you still need to use my site to sort by other attributes there is a simple technique that will allow you to do so:
Credit - Addison H.
This application is only designed to order videos within a playlist, rather than collections of playlists.
I've had a look into this and there doesn't appear to be a way to control the order these items appear in.