I think so, if not it is possible to add them to it manually without too much grief.

Each planet has an owner and homeworld property.

When you edit the players you can set their starting resources. You can change the artifact density from the main menu (when you don't have an object selected), or you can manually add one to a planet by adding a planet group to the planet, adding the artifact you want, then using the settings "Always" and "NoOwner" as parameters.

Put it in your C:\Users\User\Documents\My Games\Ironclad Games\Sins of a Solar Empire Rebellion\GalaxyForge folder.

Mine has them listed but no graphic icons. Check your file integrity through Steam.

how do I put my Galaxy into the game through steam?

whats the difference and meaning of fair in the editors in game and forge ?
e.g.
Terran vs Terran fair.
?

Don't forget the militia are always the same. No more getting a terran planet with 4 heavy cruisers guarding it while your opponent only has 1.