As far as I have investigated so far, every Speedtree imported in UE4 has 7 map channels, and I strongly believe the 3rd (2nd if zero based) is the one, or at least the main, that contains the info for the speedtree wind. Once in UE4, you can export the mesh to FBX, which doesn’t scrap the map channels, they still exist and are correct. Alas, once you import the mesh back to UE4, you can no longer apply speedtree wind to it, though it appears it has everything needed for it. I think there is a hidden “switch” to allow you to use the speedtree wind only with speedtree imports. If so I find it very constraining.
If you link Speedtree node to VertexInterpolator node, and then plug it to the base color of your material, you will visualize the offset of the vertexes in RGB, or at least that is how it appears to me. If so, I should be able to pick that offset from a certain vertex of the speedtree mesh, and apply it to the material of whatever I want to attach there, if I ever manage to run Speedtree wind on non speedtree mesh.
But way easier it sounds to me to find the exact location of the vertex, after it has been offseted, and just move the attach there.
Is it even possible? And if so, is it appliable, performance wise, since it should be done every tick, even if its just for a vertex.