There are many ways to do this. Another possibility would be to enable/disable the secret tab depending on the state of a password.
In the attached simple demo (LabVIEW 7.0), the third tab is disabled unless the correct password is entered. If there is no activity for one minute, the secret tab will automatically be disabled once again.
(Of course the password could be also obtained using a password dialog after pressing a button named "Administrator Login" for example. In a real world example, you might also want to encrypt the password strings or use a more advanced authentication algorithm.)