How to create/choose different materials for mobile vs PC version?

I have a number of materials that can be fancy, use refraction, per-pixel lighting, and such, on PC.
I’d like to use a simpler material with some effects baked into the source textures on mobile.
However, I can’t find any place in my project where I can say “on mobile, use THIS material, on PC use THIS material” for various meshes or blueprints.
(Obviously, I don’t want to switch at runtime, because I don’t want to bake/ship materials and textures to a platform that will never use them.)

How should I go about this?

Four-day bump. I think this might be an important thing to do for good mobile performance. Am I wrong? Does nobody need/do this?

There’s a “switch by feature level” node in the material editor – does that automatically exclude textyre maps that are only reachable by “other” feature levels when cooking?
It also makes for a mess inside the material when each input map is split into two separate expressions.
And, this is the worst bit: I can’t find a way to “not include” certain maps for certain feature levels. For example, if I don’t want a normal map by default, but want it for SM4/SM5, I get an error in the material compiler.