There are several sources of links in Autodesk Navisworks: original links that have been converted from the native CAD files, links that have been added by Autodesk Navisworks users, and links that have been automatically generated by the program (for example, selection set links, viewpoint links, TimeLiner task links and so on).
The links converted from the native CAD files, and the links added by Autodesk Navisworks users are treated as object properties. This means, you can examine them in the Properties window.
You can also use the Find Items window to search for them.
All links are saved with Autodesk Navisworks files so that as the model changes, the links remain there for you and others to view.