I second that. Well almost perfect. The menu background is not skinned. And Titlebar Text still missing.
Stardock Community Assistant
The Title bar Text shows if you have Firefox in full screen mode. Not sure if it is the same in a vanilla Win 10 install though.
And out of curiosity, what menu background are you referring too ??
There is a couple other browsers to skin well with WindowsBlind too, don't recall all their names but they are based on similar architecture as FireFox. Like Waterfox and a couple others.