In the External References Manager, you can view a list of external references that exist in a product and examine which items (such as faces and edges) are involved in each external reference.
Context:
Note:
In the design tree, indicates items that have external references.
From the Assembly section of the action bar, click External References Manager.
In the dialog box, click Update All References to incorporate any recent changes.
In the list, you can do the following:
Expand items to see geometry involved in the external reference.
Select items to highlight them in the design tree and work area.