You can use Creo Expert Moldbase Extension to create and delete subassemblies. Each subassembly consists of a skeleton model with all the major datum features of the main assembly. To modify the skeleton, the EMX main assembly must be the active assembly.

When you place a new component in an existing subassembly, make sure to set up the subassembly structure first. You cannot move a component to another subassembly when you modify it. First delete the component, and then recreate it.