Hi Galen, it sounds more like you're talking about old
projects not workspaces -- if it were another workspace that is like a whole other world. And you can only see items from one workspace at a time.
That said, it sounds like you need to just set your project scoping at top right. Select the new project you're working on, then choose whether to show items from parent/child projects. That will set how much of and what you see. Learn more about project scoping at
https://help.rallydev.com/change-project-scoping.