Once https://connect.mozilla.org/t5/ideas/shortcut-for-different-profiles/idi-p/707 is implemented, I would like to see something like how Multi Account Containers works with assigning URLs to a container, but at the profile level. For example, I of course use an ad blocker for everyday browsing, but when I shop I like to click through those cash back portals. Ad blocking and all the built-in privacy features interferes with how those rebates track. What I did in Edge was create a separate profile with just the few extensions I'd need for shopping purposes, and the cool thing they let you do is define a list of URLs that will only open in that profile from now on so you don't even have to remember to open a new window with that profile.