Mute
 

A hotkey, button, and a code for skins to Mute. Also, a hotkey to exit would be good

you can define hotkeys for mute and exit (among others) in preferences --> key definitions and winlirc

default for mute is ctrl+M
there is no default key for exit any more if I remember correctly (except the 'windows-wide' alt+F4)

The mute function in fact lowers the volume to 0% (it's not a toggle).