[WCSTombs]

I've also been using it for years, and it seems to work exactly how it should, but it does seem to be a bit of a "hidden feature" in my opinion. It wasn't super easy to figure out that the feature existed and how to use it.

[notpushkin]

There’s also containers, which probably covers 90% of use cases for profiles: https://support.mozilla.org/en-US/kb/containers