Context

I am trying to run Mumble on my Steam Deck in Game Mode (Valve's Gamescope Wayland compositor). Everything is "fullscreen" by default in the sense that you only see one window at a time, but it stretches windows to fit the screen at the size they are, resulting in small windows looking a bit low quality. This can be worked around in some programs like OBS by using the fullscreen keybind (F11 for OBS) which then makes it fit to the detected resolution instead. The resolution can be set for each game/application in Game Mode, but there is no way to "maximize" a window, unfortunately.
If there were a keyboard shortcut I could bind it to buttons on a gamepad in Steam Input.

Description

I would like to see default or at least optional keybinds/shortcuts/hotkeys for fullscreening the Mumble window.

Mumble component

Client

OS-specific?

No

Additional information

An alternative could be a special launch option for fullscreen, maybe.