when you save a complete structure into you workspace with the uwgm for creo elements/Direct Modeling, you should be able to set the view of your workspace in that way you only see the top assemblies of the structures you saved. This will provide a powerfull overview when you work on several structures simultaniously. If you want to continue your work the day after, you simply go to your top structure and load it. you are not bothered by other models that are in some substructure, because you only see the top assemblies, and don't get a list of thousand and thousands of parts, where your top assembly is somewhere amongst. you should also have the ability to navigate down your structure, while you are in your workspace. This is functionality that is common in Creo Elements Direct Model Manager, and is indispensable for a customer which would want to replace Model Manager by Windchill.