While a bit nervous about installing and using an addon with so few users at the time of writing this, it does work very well. I've encountered no performance issues, the "left shifting" works and no wonkiness even using different themes.

UPDATE: sadly stopped working as per 08-2024. Annoying mixes again showing up all over the place.

UPDATE to the update: works again, intermittently, after a new version. Seems like the usual game of whack-a-mole between addon and YT. It will work, then refresh/reload screen, mixes show up, repeat, mixes gone. And on and on.

To the author: good luck!