I've been looking for a way to sort my watch later by duration for AGES and at first I didn't think this add-on was the right solution for me, as the free version only sorts a small batch (about 100) of videos in the watch later playlist so if you change the organization to oldest for example you lose the duration sorting, but I paid the $5 CAD for the Patreon and its become the most worthwhile thing I've ever found

You get a playlist made for you, sorted by duration, in only about a minute or less. The most beautiful thing about it being a playlist rather than a small sorted batch of your watch later is I can watch it on my phone or my laptop.

I haven't tried to other features yet, but so far I'm super happy.