Planet Bonuses in Galaxy Forge

I appologize if this has already been gone over somewhere but in my searches and in the intro guide it didnt say.  and i cant figure it out on my own.  How do you put specific planetary bonuses on a specific planet in Galaxy Forge.  I see how to set a general probability of there being bonuses in the system as a whole.  But not specific ones.  I want to make a cirtain planet have a smaller mass for a smaller grav well.   Or a different one have reallly high trade.

Also how do you set the number of mining astroids a planet has?  please tell me there is a way to mess with all these thigns.  If it were truely all randome and preset that would kinda suck.

And also, i figure this probably needs to be done messing around with code not in Galaxy Forge, but is there a way to physically change the scale of a planet.  I want to make one planet apear alot smaller then another.  Ex:  Venus and mercury are both "volcanic" but one is alot bigger.  is there any way to change the scale?