The drop down box allows you to select any linked workbook or to type in all or part of a workbook's name to find related links. If you have links that you can't find, you can find them with the Link Finder. You can also delete them either automatically or on a case by case base. The Link Finder also provides a selection dialog that allows you to quickly go to any link it finds. If used to modify links in workbooks belonging to other users, a license is needed for each such user.
Site licenses are available.