After you have excluded (Tools > Exclude) Reference 3D objects, you can create a workspace that contains only those excluded objects. This allows you to review them at any time and use Tools > Include to reload any excluded Reference 3D objects into the workspace.
If you define a workspace with a filter that allows both included and excluded objects, the Include and Exclude commands are not available on the Tools menu or on the shortcut menu. You must change the filter and remove either included or excluded options for the related command to be available.