In Float Layout I miss Shortcut for "Fullscreen active Window"

[bugfrei]

Is your feature request related to a problem? Please describe.
If I was on Float-Layout and I have a small Window, I want to maximize that (fullscreen).
Actually the only way ist to activate fullscreen-Layout and switch back to the Float-Layout. But then ALL Windows are maximized :-(

Describe the solution you'd like
A simple Keyboard-Shortcut that maximize the actual focused window.
In other Layouts this Shortcut can do the same like switch Fullscreen-Layout (or back) so I can maximize the window if I in Float or any other Layouts (but in Float maximize only the active window).