Tabbed semi-transparent overlays to reduce space usage

Hi!
I have an idea to present more information on the screen with reduce space usage. On top bar, you can:
a) Hide some information, by putting it onto tab
b) Use semi-transparent overlay with z-index of widgets, so semi-transparent tabs (without labels) will be displayed on top of urbar and navigation controls (possible others); it also requires to use tabs

Tabs will be displayed, when user move mouse cursor above top panel. It will be displayed below the container (floating). Additional, hide/show button will be displayed near tabs. When taopbar is hidden, only unhide button will be displayed to bring topbar visible.
Tabs will be centered to x-dimension of mouse position.

About overlays: I think user don’t need to see tabs title - we can only display active tab in different way, as currently. Of course, you can display title, but with y-dimension offset.