[msclrhd]

See https://www.userchrome.org/megabar-styling-firefox-address-b... for details on how to customize the new address bar, including userChrome css for keeping its size confined to the dropdown UI like other dropdown/combobox UI elements.

[jamoes]

Also see https://superuser.com/questions/540851/go-back-to-not-select... for details on how to disable the clickSelectsAll behavior.

This issue is frankly far more important than the style changes they made. It's a muscle-memory issue that drastically affects daily usage. I was so desperate to restore the sane behavior of not selecting everything on a single click that I was recompiling firefox prior to discovering this workaround.