Wheneven I create a primitive or import a mesh, the default “Diffuse” shader is automatically applied, I would prefer it if “Mobile/Diffuse” got applied instead. Is this possible?
Do you mean just as a default so its an easier workflow? I don’t think so, at least not built into Unity… If you store all of your materials in the same folder though, you can select all of them and apply a Mobile/Diffuse shader to all of them at once. Hope this helps.
You can add new entries in the create rollup with AddComponentMenu. Inside, create the primitive (GameObject.CreatePrimitive(…)) and affect your material. Then clic on whatever name you’ve set instead of the regular primitive.