you are right you can only create static meshes with the foliage tool and I don’t think you can access the static meshes through blueprints to get rid of them or even find their positions.
here is a thread that is trying to answer a similar question. Removing single instance of a foliage actor? - World Creation - Epic Developer Community Forums
I am making a game where you play a dragon and I want to make destructible forests, that you can smash or burn through but I cant see how I would do it yet. here is a video of my game, Unreal Engine 4 Dragon game prototype - YouTube