Feature suggestions:
1A. Add Master Volume slider to Game Launcher Settings. Would be easier to change the in-game volumes all at once. This, or:
1B. Make it so that if you hold Shift while sliding any of the volume sliders, it would adjust all sliders at the same time.
2. Add a hotkey "m" to mute all in-game sounds during gameplay. This would be handy, if for example watching streams or listening other music during gameplay.