3dsMax Datasmith exporter - collision defaults to simple

Having used the Datasmith exporter modifier in 3dsMax on a number of objects to specify a custom collision object, I’m surprised to find it defaults to just a simple collision mesh, rather than the complex collision mesh I modelled and pointed to. I assume the custom selection of a collision mesh from my 3D package works similar to the UCX collision method within an FBX file. The custom mesh is not available in my geometries folder, in fact I can’t figure how to change the simple collision generation in the mesh details for the stairs.

I’m finding Datasmith comes with plenty of distracting quirks, please don’t tell me to report this as a bug, just tell me what I’m doing wrong, or if it is an actual problem that I need to find a workaround for, which I already have done, though probably not the most elegant and not a solution to this.