Wouldn't it be easier and/or faster to create a userscript? I've "vibe coded" tens myself, but never really saw the use case for making a full extension out of any of them. Genuinly curious what you made.
Another one (I've open sourced, you can check it out here https://github.com/luvchurchill/mani-gpg) A site I use (manifold.markets) announced they are getting rid of DMs due to spam (they've since brought it back) so I made an extension which makes it easy to use pgp & age encryption on the site so we can do pseudo DMs. It injects "Decrypt" buttons next to exncrypted text etc etc. You can see screenshots at https://manifold.markets/post/an-extension-to-assist-with-so...
(Look at the comments for the latest look)
Besides for that, there are a few I'm sure can be scripts