On the “on playing screen”, I that possible to add the following things ?
% of volume level close to the + button,
A button to switch on/off the loudness . I know we can go to the sub screen for that, but this is not easy to find in the list of settings they are in.
A button to mute, may be would be better to have it on the main screen.
It won’t give you a loudness toggle, but I agree with what @Wheaten recommended, the Now Playing plugin. This gives you huge frredom to play with screen layouts … including % volume.