When you are adding videos to your playlists Sometimes you don't remember if you've already added that video. This script puts an H button next to the search bar to Hide videos you've already added to your playlists, so there are no duplicate videos in your playlists.
Now it works with all user lists, including watch later, just add the id of your playlist on line 31 of this script var index = ["WL", "PLo29ME-MyPlAyLiSt-0vukQAqlG6R"]; separated by commas and quotes.
They usually start as PL
https://www.youtube.com/playlist?list=PLo29MExxxxxxxxxxxxxxxxxx.
WL is the playlist watch later
Now no APIKEY is needed.
