@leocg Is there any update on this feature? Roadmap? anything?
This is a critical feature, for so many reasons. It should be implemented in a way similar to Chrome, not like Firefox. Firefox has some pretty serious cross-communication between different versions of firefox and browser profiles. The profiles can become corrupt if you use Fx canary and Fx regular on the same machine. Also, the Firefox user experience is abysmal. You can't switch profiles without using a hidden browser feature: "about:profiles" and this interface is ugly and visually overwhelming, requires too many steps to use, and is not discoverable. It's more of a dirty work-around for proper profile support.
So you may ask, why is this feature so important? I use different profiles in Chrome to manage completely separate sets of credentials, bookmarks, and identities for work and personal. The only problem with Chrome is that it automatically advertises the username of the user and you cannot mask a username, so you cannot register anything with sensitive information, if you intend to share the computer with anyone like children or a spouse, or if you ever share your workflow with co-workers or students via screencast.