The toggle UI function (default `~ key) toggles the action bar on and off on demand. This function should toggle the entire UI on or off, including messages (server & chat) and weapon HUD. Besides potential immersion enhancements (getting a completely clean view whenever desired), it would greatly enhance the ease and quality of screenshots. Look at KSP, for an example of this function - F2 in that game will toggle ALL UI elements on or off.