Pin as App Tab does not stick permanently
Pin as App Tab works for a day or two then disappears and I have to redo it. My favourite is GMail but it doesn't stick for long.
mha007 Thx for your post & apologies for lengthy delay in replying. I don't think Session Restore is needed now as I just installed a GMail button on my Fx Bookmarks Toolbar as a backup. Regards.
It is always best to use "Firefox/File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit") to close Firefox and to close all open windows at once to make sure that there aren't any (pop-up) windows left.