Concatenate your model from thousands of distinct elements to one unique GameObject with a single material, to drastically reduce draw calls.
The Combine function creates one mesh with one baked material from a set of different meshes with different materials assigned. It will not produce any geometric changes. The original UV are preserved but repacked into a new unified texture atlas.
WARNING Combine Mesh is rather a long function. Please expect a long execution with large input.
NOTE Combine Mesh has been tested and validated through optimization processes containing meshes with standard materials.