I'm still testing it, but it's pretty good.
It's much easier to press one button than to constantly go into the menu.
Right now, I only have ONE problem with it not working in the Firefox Container Tabs, since I use several YouTube accounts and separate them.
I also really like that permissions are limited to YouTube sites only.

Restores this useful function if you'd rather not disable video previews. Being able to set opacity and to always be visible or only shown upon hover gives you the option to finetune to your preferences. Does not work with shorts.

Not working with new Youtube UI (transparent low bar). I used greasemonkey scripts before but now neither scripts nor this add-on work :(
What I mean is: no matter if add-on is present or not, I can add video to watch later on youtube pages when I hoover over different video recommendations. However when I have video currently playing, I cannot add it - there is no button in top right or left corner of video.
For now I disabled all scripts and add-on and only use default youtube buttons - when I want to add currently played video to "watch later" list I have to use "save" button first, and then select "watch later" playlist. There is no way to do it in one click on new UI.

very neat! but i feel like you should:
- fix this bug where the button in notification doesn't appear for some notifications if button visibility is set as hover
- make the button use current color in watch page because i'm using a custom YouTube theme
- i know im asking a bit too much but can you add the button in the shorts page?

I like to middle click a bunch of videos and have a bunch of tabs. Would be nice to have that watch later button on the actual video itself instead of ONLY the thumbnail.

works as intended and loads faster than youtubes own buttons

Edit: found that on rare occasion "exclusive access" blocks the button as they are in the same corner

2nd edit: Thank you! Hope you keep maintaining this add-on in the future as I will probably use it as long as it works :)

Freezes when saving sometimes but the mere fact that the must-have button is back on youtube is absolutely great! Thank you for your work!

So glad I found this addon. I was middle mouse button clicking thumbnails to open in a new tab which is not the best workflow. I have been wanting a button on the preview that adds videos to watch later with one click. This does that. It also clearly marks that it has been added. Exactly what I needed. Thanks!

Exactly what I needed. Would love an option to change the position of the button on thumbnails, it's layered under the SponsorBlock icons for "exclusive access" and "unpaid/self-sponsored" videos. Not unusable, but mildly inconvenient.

edit: Super quick response from the dev, would give a sixth star if I could lol

You hit the button and nothing happens.