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.

The only feature I want, block channel, doesn't work for me.

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.

Installed this just for the "reverse playlist" function. :-D
Lot of other goodies.

字幕が常にオンになるのだが？

For the most part, this extension is amazing, definitely helps with combating YouTube's auto quality setting too.

This extension is missing out on a lot of the updates from its GitHub repo however.

If anyone is coming across an issue where you can't re-enable comment avatars try this:
#1: Go to "about:devtools-toolbox?id=%7B3c6bf0cc-3ae2-42fb-9993-0d33104fdcaf%7D&type=extension"
#2: Click "Storage" from the top if it hasn't been selected already
#3: Open "Extension Storage" from the left side
#4: Click on the first result
#5: Click "Filter Items" and type "hide_author_avatars",
#6: Right click on the first result and click "Delete hide_author_avatars"
This should bring back comment avatars (you may need to reload existing YouTube tabs)
You do need to delete the key since setting the value to "false" doesn't work on this particular version of Improve Youtube (3.935).

Criminally underrated... It's the best all-in one add-on for youtube in the store. Everything fits perfectly!
Also, in most add-ons you can tweak the volume but it sets the playback speed to default and cant be changed while using it. So I think it's syncing with the changes here.
>
The only issue i have is that if the header is set to hover, it creates a gap between "suggestion categories bar" and firefox address bar. I hope in the next update either both will be hidden or the suggestion bar will be replaced with the header while hidden.
And maybe there will be a dark mode for the add-on as well.
Another thing is, maybe this add-on isn't marketed quite well. It took me a while to find it. Should have been the top search result.

Great open source alternative to Enhancer for YouTube, but my only issue is that theater mode doesn't seem to enable automatically even with Forced theater mode enabled.

The customization is amazing and I would absolutely be using this all the time except for one pretty big thing - it seems to be resetting my theme to dark mode no matter how many times I switch it back to light. I understand that most users prefer dark mode, but on YouTube I do not and I find this very irritating. Uninstalling the extension fixed the problem. I wasn't sure whether to give this 3 or 4 stars because the error I was having was so irritating, but everything else was good so I gave it 4.