Thank you Alex I’ll try thoseI didn't catch the original conversation but I'm gonna guess Stylus, which allows you to modify a site's CSS styling: Firefox Chrome Github. Aside from uBlock Origin it's my most used extension.
If you want to modify a site's Javascript then probably Violentmonkey is the main open-source extension for that (Greasemonkey is the original but was dormant for a while; seems like it might be picking up again).
Statistics: Posted by RicardoTM — Today, 7:34 pm