If you have administration rights to a Workspace, you can make it inactive.
You configure active Workspaces in Configuring Workspace Options.
If a Workspace is inactive, it will not appear in the My Workspaces section of the Collaboration Panel. The only way to open a closed or inactive Workspace is to search for it in a Workspace Retrieval and open it from the search results list.
See Using Workspace Retrieval to Find a Workspace for details.
Note:
Once you elect to make a Workspace inactive, and click Save to save the setting, all Workspace Options will be read-only until the Workspace is active again.