YouTube Playlist Tools Cephalos מאת

• Automatically add the current video to one or multiple playlists
• Set a required watch percentage before it gets added
• Set a custom shortcut for it to be added to a special playlist
• Optional toasts for extension actions

To use this extension you need to supplement your own credentials.
Follow the steps in the github readme if you don't know how.
https://github.com/Alioun/yt-playlist-tools