Delete flexible space around address bar for FF60 esr
By default FF57 has flexible space around the address bar (and I assume this will be the case with FF59 esr too).
Onion addresses will be 52 characters long at that time, the window is also only 1000px width long, and so it may be better to delete that flexible space.
Tagging ux-team for their opinion :)
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information