I appreciate your reply. This product would be convenient if you can fix the file path and size problems on Mac.
The number of some objects in my objects appear quite frequently. (walls, grass...) Fortunately, there are no many such kind of objects in my project. Using this product already can greatly reduce the number of tris, and I know how to paint them. Thanks for letting me know that the Magicavoxel textures are not easily supported, I was about to waste my day on it.
By the way, I did not mention that I had problem importing FBX file genereated by this product to blender. The error was "ASCII FBX files are not supported". However, I succeed in importing them into blender using some mesh combine add-ons via Unity.