Nice! Like older firefox extension to do site customizations.
I think strange separate tab for configuration, maybe more easily on the page(Over)
And complex to do configuration... But cool.
And that problem:

17:10:14.762 TypeError: localStorage is null D5S6p27u5t8:11:214
https://www.youtube.com/embed/D5S6p27u5t8:11
https://www.youtube.com/embed/D5S6p27u5t8:11
moz-extension://e78eb895-53d3-4535-84ac-eaeb403d6b63/embeds.js:32
apply self-hosted:4419
applySafeWithoutClone resource://gre/modules/ExtensionCommon.jsm:539
applySafe resource://gre/modules/ExtensionCommon.jsm:526
applySafe self-hosted:1007
wrapPromise resource://gre/modules/ExtensionCommon.jsm:740

Great tool for handling some of the more annoying crap that YouTube bugs us with.

Doesn't work very well.

I had the 'pause video in background tabs' selected, but then when i would click on that tab, the video was still paused (i did not have the 'pause foreground tabs' selected), it doesn't autoplay. (and no i don't have autoplay disabled)
Also the whole feature itself is pointless since videos opened in background tabs are paused anyway, i think it's a feature youtube itself implemented at least 6-12 months ago (at least on Chrome)(to save bandwidth and to make sure you watched those ads) and then they autoplay when you click on them, just as they should.

When the video ended it would loop, even though i did not have that selected.

Then when i came here to write this review i saw that the +Add to Firefox button is still blue, so i clicked it, which i guess uninstalled the "old" one and reinstalled it ?
Now the video doesn't loop anymore, in fact i can't find the loop setting anymore in the settings (it's still in the toolbar), so maybe it got an update.

The default volume level setting is fickle, sometimes it works, sometimes it doesn't. Which is a shame cause that is it's best feature.

The description to the Remove Ads button says that right clicking on it disables Annotations, this again doesn't seem to work, or at least it doesn't toggle the setting in youtube and i couldn't find a video with annotations to test it. Also you can just disable annotations in the youtube settings, not sure why this is even needed.

In fact i'm not sure if the whole extension is even needed, it just doesn't do many useful things, for me anyway, and what it does do, doesn't work consistently, how this got featured is beyond me.

Also the +Add to Firefox button is still blue, does that not change to a green "Already added" button ? does Firefox/Mozilla not have that ability ?

Really cool Add-on! Youtube has way to many UX restrictions, and this add-on is a must if you like to spend time on Youtube :)

Cool way to enjoy YouTube!

Works great!

I like the feature that pins the video when we scroll down and the video quality select mode.

Thank you!

Was pleasantly surprised that this works so smoothly
(whithout slowing down anything else like other add ons...)
Thank you Maxime R.F.

Great

thank every one for the help and not running me out on rail

This is great! So greateful i came across it.

.

Great features and works reall well. Would highly recommend

очень гибкая настройка, множество полезных (и не очень) функций. работает стабильно и быстро

10/10 Best youtube extension, would recommend.

Good

Excellent in terms of features and flexibility - the best YouTube add-on I've found for Firefox.