I would like to add a trusted a path in the global preferences of Mathematica. When I go to NotebookSecurityOptions, click the tool button for TrustedPath, and click 'Add', a dialog box appears and asks for a path.
After reading the official documentation on Notebook Security, I still have no idea how to enter a simple, specific path (eg ~/Desktop) into that box. I can't find a documentation for the Filename function as well, so I'm left with just guesswork. I have tried several guesses in vain.

FileNameSetter[Dynamic[f], "Directory"], if that helps. – Michael E2 Jul 21 '13 at 01:26