There are a few ways! I have separate Firefox profiles for everything.
The least effort way is to visit about:profiles, then you get a list of them all and can add/remove them. I have it bookmarked or pinned as a tab in all of my different profiles.
Second, but takes more effort is you can make desktop or start menu shortcuts to the profiles. In short (on windows at least) you copy the Firefox shortcut, edit it, then add -p “Profile Name”. There might be more to it? Maybe good to Google this one for a better description. But I literally have a start menu shortcut for all like 7 of mine, then it’s just like launching a different application.