@Elvizon
The builder is for more lower level concepts for the programmer, you would need to create your own sandbox / build system that utilizes Unreal buildings tools.
That being said, the marketplace and Quixel are full of already modeled structures, so please feel free to check those out:
But to place them in game and save their locations, and to provide players with the necessary freedom of the genre, you would need to make your own system.
I hope this can help!
-Zen