A good program

I might be wrong, but I'm pretty sure that in order to modify maps you have to export them into a 3d model and then edit them using a 3d editing program, such as blender, and then reimport them. I'm no too familiar with 3d modelling other than in vector works, but I think it would be quite advanced. Not only that, but you also have to use a rom, and hgss often glitch on emulators raw. 5th gen Roma can lag quite a lot as well. Platinum could work though