The Custom Firefox Button somewhat overlaps with the tabs underneath. The screenshot below is from testing with the default settings for Hide Caption Titlebar Plus, running in a clean test profile for Firefox Developer Edition 56.0b2, on Fedora 26 Workstation x86_64, with GNOME Shell 3.24.3 in an X11 session.
This bug is a little inconsistent, though. The other day, when I'd first installed the extension, it was even worse, so that the button also partly covered the page title in the titlebar.
The Custom Firefox Button somewhat overlaps with the tabs underneath. The screenshot below is from testing with the default settings for Hide Caption Titlebar Plus, running in a clean test profile for Firefox Developer Edition 56.0b2, on Fedora 26 Workstation x86_64, with GNOME Shell 3.24.3 in an X11 session.
This bug is a little inconsistent, though. The other day, when I'd first installed the extension, it was even worse, so that the button also partly covered the page title in the titlebar.