Great, would love the ability to hide mixes, and have more videos per column if possible.

Almost too good to be true. But so far, it seems it is.

The main reason I wanted this extension was to make Youtube stop spamming already watched videos, random playlists and useless shorts.
1) It doesn't block already watched videos, it just makes them less visible by hiding the thumbnail and dimming their links;
2) Sometimes it marks random videos as watched, but I never even clicked their links, even less watched them;
3) It cannot block playlists, as far as I used it;
4) It blocks shorts successfully AND entirely (not just dim their links).

Great extension and much lighter than the enhance youtube extension which is also great but slows down the system. I prefer this one