I have a feature request for MCreator - improving the biome floors. I feel it would be very useful to be a ble to chose multiple blocks for the biome floor - an it would make custom biomes look much better. This could be created in a way similiar to the program world painter - the player can pick multiple custom and blocks and give the a chance out of 1000 for being the floor block. For example, for a taiga biome it might be 700 Grass and 300 Podzol. It also allows 2 types of generation - blobs (with changeable size) and random noise. I reccommend you check out this program and see if you can implement something like this into MCreator.
Thanks :)
Issue comments
Although the idea is very nice, the actual implementation would be out of the scope of the current implementation of MCreator so we can't add something like this.
You can make ground of multiple blocks however using the hack posted here: https://mcreator.net/tracker/issue/46422
One easier way to do this would be to allow players to import worldpainter .terrain files