Any OPC AE behaves in such a way that Alarm generated from Controller-OPCAE-Alarm manager to display -once alarm ack-OPCAE-Controller FBD (to ensure ACk).
In general If PV crosses the limits then alarm will triggers and based on the Hysterisis, alarm will remain in active state and once crosses Hysterisis alarm will be normal.
Can you give bit more info. what you are expecting as re-alarming and what situation you need these things.
The functionality can be achieved by creating a custom object type that embed a regular AlarmCond block and monitors its condition state (CondState) and if left at Active Acknowledged (state 4) for too long time (measured with a Timer and compared with a parameter like "MaximumAcknowledgedTime" defined by the custom type) cycles the Signal parameter of the AlarmCond block to fire a new Active Unacknowledged alarm (state 5).
The default action in the 800xA HMI alarm lists is to remove the previous alarm and replace it with the new. Event lists, however would tell that the block briefly entered Inactive, Acknowledged (state 2) and in the next split second goto Active, Unacknowledged. This temporary "return to inactive" transition is not completely true from a pure process perspective since it was your "Re-Alarm" block that cycled the trigger signal to force a new alarm.