Curious how is this better than using multiple profiles (config:profiles) to isolate one set of behaviors from another? I’ve been doing that for years.
You can't run two profiles concurrently can you? I have a container for finances, a container for shopping, a container for untrusted, etc... I can't imagine restarting Firefox every time I wanted to transition between those.
I use different themes for each so they are visually distinct.
And different home pages, etc.
I could use different shortcuts for different identities, but I don’t any more. Instead about:profiles is one of my home page tabs for each profile.