[detaro]

I think you can already do that?

[wink]

Yeah, just start the profile manager (firefox --ProfileManager), create a new profile, and then run the "other instance" with --profile NAME. Sometimes --no-remote is also helpful, so clicking on some links will not open them in this other profile.

[Vinnl]

This can also be done from within the browser: navigate to about:profiles.

[bauc]

You can, if you run Firefox with -P and profile name. I run two instances most days.