Prop assembly assets are hierarchical collections of prop instances stored as a single asset that can itself be instantiated within the scene.
Create these assets from within the RoadRunner Library Browser.
Refer to the Library Browser page for general instructions to create, edit, and delete assets.
A new assembly asset will appear in the current directory of the Library Browser. Rename your asset as you see fit.
The selected prop node will be automatically replaced by this new assembly.
After placing a prop assembly instance in the scene, you can expand it to separate it into its individual components, which breaks the instance's link to the prop assembly asset).
This is useful when you want to modify only a single instance of the assembly. For example, if you want to move a traffic signal head on a traffic assembly.
Select the Prop Point Tool.
Select a prop point with a prop assembly assigned to it.
Click the "Expand Assembly" button.