Advanced Editing of Custom Biome Terrain?

I am working on a custom biome that requires for some more detailed terrain than the MCreator Workspace ((appears)) to be able to do. For example, I want the terrain to have many small pools of shallow water with a floor of sand/block. I also would like the predominant surface block (grass) to have large, scattered patches of a different surface block (gravel); all of these naturally spawning.

I'm new to modding and I want to know if I can do this with the MCreator modding toolkit.

Thanks much.