The only magic systems we know less about than the Breath magic system are Hemalurgy (due to the complexity of the human body and its bind points) and AonDor, because Sanderson doesn't want to go through the work of making all the modifiers for Aons, including the ones that make the Aon work like programming (i.e. If someone steps here, activate Aon Tia and send them to the dungeon)