Currently, Supports can only be placed on Foundations. I have seen amazing looking builds where foundations have been placed underground so that pillars can support structures like balconies without looking like they are over foundations, but pillars being able to provide support directly from the ground would make balconies and bridges both easier to make and more visually appealing. In other games this has worked by allowing the pillars to snap to the underside of floors/other pillars and they don't provide support until they go all the way down to the ground.
