Option to hide Titlebar with Tabs Sidebar active

[aschroeder27]

Is your feature request related to a problem? Please describe.
I'd like to maximize the available vertical space.

Describe the solution you'd like
An option located under Settings -> Tabs Sidebar -> "Show Window Titlebar when Tabs Sidebar is active".
When active, the Titlebar would be hidden and the window contol buttons could be added to the left side of the nav bar.

Describe alternatives you've considered
I've tried to achieve this behaviour with userChome.css but that doesn't seam possible.

Additional context
I'm using macOS.