i created my material instance from stone_wall_material. After i created the material instance , i replaced the albedo texture with a mossy concrete texture (which i got from MegaScans; unlimited free with Epic account ; with Unreal Project use only).
I also created additinal maps ; roughness, normal and specular uses red channel of the albedo, I also create parameters for each so when you create a material instance you can adjust them without changing the master material. I also added the U,V parameters shown in the class.
The gray area are comments, it groups so it is easy to understand what is going on. To add comment you select an area that has parameters , functions…etc and hit C on keyboard and it creates a grey area and you type the definition. I learned this from Quixel / MegaScans youtube video which i posted earlier.
Note: MegaScans has also a plugin that export meshes and textures directly into your project and also it creates master material and material instances for meshes. That plugin was broken in UE4.25.2. But it works with the new update UE 4.25.3 which was a fix for all MarketPlace plugins were not working. For this project i did not use yet but i will add a Light fixture later :)