Title. There is one (one that is dead and was made back in the 2.0 era (and was for connecting physical hardware), but still).
Also, I'm not talking about Scratch extensions (pen, etc).
edit: broewser -> browser

could you possibly link it or tell the name? if it's by the scratch team no doubt it would be ok to say

Yeah, if it's made by the scratch team I don't see why you couldn't.

The userscript policy deals with non-ST extensions. People are allowed to say Scratch Link, which is a literal app for connecting to physical devices, but since it's made by the ST it's allowed.

also hi CST

I think if it was created by the Scratch Team, it shouldn't be a problem.