Extension cannot be used with brand accounts

[MmyGgithubAaccount]

This extension seems to only be usable by the main google account and not youtube brand accounts (#5 (comment)) for which auth tokens cannot be retrieved. I only use my brand account to watch youtube so the main account doesn't have access to my brand account's private playlists. Making the playlists unlisted is an option but that doesn't work for auto generated playlists like "Your Likes". I tried adding the @pages.plusgoogle.com assigned to the brand accounts as a test user but that doesn't work either