When features are unavailable (grayed out or dimmed) in the Remote Desktop Admin application, the application is probably being run in Non-administrator Access or User Mode.
User Mode was introduced in Remote Desktop 2.0.
Non-administrator Access or User Mode is activated when a non-administrative user opens Remote Desktop to administer Apple Remote Desktop client computers. The administrator of the computer with Remote Desktop Admin installed can choose which features and tasks are available to non-administrator users.
See the Apple Remote Desktop Admin Guide for more information.