After I import an FBX model with the [x]combine meshes option it will have e.g. 20 elements (surfaces).
Each of those elements is a different kind of glass object that should use the same GlassMaterial.
I can apply the GlassMaterial one by one but this is tedious.
I tried various ways to multi-select all 20 elements (so I could apply the GlassMaterial to all selected elements at the same time) but this does not seem possible.
Ideally, in your modeling package you would want to combine these meshes so that it uses a single material ID rather than combining them on import. This will just create extra draw calls that can hinder performance later on in your game.
This is not an ideal solution, but you could set up something in Blueprints in the construction script so that the material is applied to each element, but that would take more time than just assigning the 20 materials to the different elements.