The avatars aka “profile-specific badge” is an important new aspect because, at least in Windows, there was previously no way to tell which taskbar icon correlated to which profile. The only way to address that annoyance was via a somewhat obscure feature to change the Firefox program icon (changing the taskbar icon alone doesn’t work as it doesn’t persist on opening the program), and that only worked by having a separate Firefox install for each profile.

Looks like the old Profile Manager might still be the go for advanced users (e.g. new UI appears to lack ability to set the folder).