Sorry but you have to be more specific. What is the "whole thing"
I don't rebuild anything.
If I want an obstacle I Add and obstacle from Single CAD file, same with parts
If I want a tool. I just go to robot UTOOL and I loaded from a file
If I want a part on the gripper, I select the robot tool, select Parts tab and added
Lets say you want a conveyor with pallets. You can ask for one single object with both of them or separated and you "build" It's t your convenience. You might even want both cases (together and separated)