Possible to change resource asteroids in forge?

 Can't seem to find how to do this in Forge.  It it possible to set how many resource asteroids orbit each planet in forge?  I'm wanting to create a map with a couple of sun systems with a poor amount of resource asteroids and a central sun system with large resource deposits.  As a related question how do you set how many resource asteroids orbit in a Asteroid belt or PlasmaStorm.  I know with those two being uncolonizable the astoroids when have to come with a neutral extractor.