Could you permanently add additional entries to the triggerhappy.conf file? The ones mentioned in my last two posts.
KEY_MUTE 0 volumio volume toggle
KEY_LEFT 1 volumio previous
KEY_RIGHT 1 volumio next
KEY_PLAY 1 volumio toggle
KEY_PAUSE 1 volumio toggle
KEY_VOLUMEUP 1 volumio volume plus
KEY_VOLUMEDOWN 1 volumio volume minus