I hear you on the editing. Unfortunately, I also use the desktop client regardless so it'd be good to see compatibility with Firefox here.
In Firefox (latest version) on both Mac and Windows computers, encrypted text in notes (when opened/un-encrypted), is uneditable (not even selecteable). It is all highlighted light green if you try to select anything in it (e.g., for copy and paste) or when you try to edit it. It almost seems to be treated like an image in that if you click and hold on any part of the encrypted text, all of it is selected and able to be drug around. Please seek a solution.