It's not a feature I use, but if you launch with "firefox --ProfileManager" it pops up a profile selection window. Maybe that's in the ballpark of what you want

It's not a feature I use, but if you launch with "firefox --ProfileManager" it pops up a profile selection window. Maybe that's in the ballpark of what you want? https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles https://support.mozilla.org/en-US/kb/profile-manager-create-...