* The Firefox (BETA) entry does not work on default Ubuntu installs, where Firefox is a Snap. Yes, snap bad, bla bla bla, but it still remains one of the most likely way Firefox will be installed on Ubuntu. This comes from the fact that your script attempts to locate the profile folder in ~/.mozilla/firefox, whereas snaps stores them in ~/snap/firefox/common/.mozilla/firefox/.
* New profiles unfortunately don't share logins on Firefox, which means your app is disconnected at first. Not a big deal, but could maybe be changed by copying some things from the default profile ?
* Firefox does not display _any_ titlebar when ran in this way.
Love the idea. There's many times where I'd like something to have a bit more "privilege" on my toolbar than what a regular tab (even pinned) gets.