This add-on contains lots of bugs. First; it extends the lenght of player so if video is 16:9 it becomes much more long in player base and i have black bars on top and bottom of the video. My YT home page and YouTube users' profile pages also broken because of this add-on. They solved lots of bugs so i am just turning it off for now, i wish they can solve new issues without any more time.
Edit: "Limit Page Width" solved the bug which i mentioned (video width and home, profile pages). Thanks. But changing thumbnail quality breaks thumbnails to gray boxes.

There's a lot of promise here, but there's no polish. Some features work great, until you move/resize the screen. Some features don't work the way you'd want them to. No volume controls for the mouse wheel. It will eventually be a contender with "Enhancer for YouTube™" but I'll give it 6 more months in the oven until I try it again.

Could you make the custom shortcuts work in another tab or while using PIP? I'd like to use rewind-forward keys from outside Youtube

No update since January 2022.

Youtube has updated her design and the thumbnails won't showing.

Please update this extension.

Disabling 60fps gets rid of HD options on the video which was the only reason I even downloaded this addon so sadly it's currently unusable for me. But the other customization options look amazing if you're into that sort of thing!

I mainly want to use this addon for the bigger cinema mode.
When player size is set to "Fit to Window" upon reverting from cinema or full screen to the small player it will extend all the way to the right and overlap behind the video suggestions there.
Looks like the addon resizes the video player before youtube changes the position of the video thumbnails.
https://i.imgur.com/MQqbQSh.png

Overall love this, however recently with the latest Firefox update, it no longer seems to work correctly, waiting on updates I guess