This read-write value enables or disables generation of the pdnStackUnitAdded trap, which fires when a new unit joins the stack, with enabled(1) and disabled(2) as the defined states. An admin toggles this to control whether the NMS gets notified in real time whenever stack membership grows, useful for tracking unplanned or unauthorized additions. For example, an admin might set pdnStackUnitAddedTrapEnable to enabled(1) so they are immediately alerted whenever a technician adds a new unit to a production stack.