YouTube Playlist Sorter (A-Z) by Jordan Heale

PSA: YouTube has had a design update since this extension was created (at least as of April 11th, 2024) that removes listing of playlists in the sidebar, moving them into a singular button called "Playlists" that takes you to a new page with a grid view (and at least, A-Z sorting).

This obviously makes half of the purpose of this extension redundant, however the "Save to playlist" behaviour remains unaffected, so depending on your use case this extension may no longer be of use. As a result, please consider the extension deprecated at this time as no future support will be given.

By default YouTube sorts the order of playlists by usage. This extension overrides that behaviour to be alphabetical (A-Z) in both the main sidebar, and the selection modal that is brought up when deciding which playlist(s) to add a video to.