I have not found a setting within the Steam mode to change input speed. I did boot into the desktop and slow down the mouse cursor there. But it does not seem to carry over into game mode.
The game I am playing does not have a cursor speed setting either.
disco@lemdro.id 15 hours ago
You need to use the controller settings for the game you’re playing. You can adjust everything in there.
nokturne213@sopuli.xyz 4 hours ago
I do not see a mouse setting within the controller settings, only for actual controllers.