Specify material elements via modo.

Where or how in Modo does one specify material elements for fbx export to Unreal Engine 4?

I am exporting a static mesh and would like to have element 0 to element N available to assign material to. I’ve tried creating Material Mask for each mesh in Modo and then exporting to UE4, but I still get only one material slot.

Got help with this on twitter.

Select the polygons you wish to apply material to, right click → set material → name the material.
There is no need to have the meshes in different layers or have any Item masks.