How can I implement the Repeating action even after snoozing/unsnoozing the target data item?
You can use the Queue until restricted option in the Action advanced tab.
Upon snoozing the cell, the repeating action is cancelled even upon unsnoozing after. The only time it will fire again is if there is a change in state/severity (i.e. cell goes ok, then critical again). If you wish to continue/resume the repeating action after snoozing and unsnoozing, you must tick the Queue until restricted box in the Actions advanced tab (see screenshot).
From the Gateway documentation: the Queue Until Unrestricted setting controls what happens when an action which was triggered while restricted later has the restrictions lifted (e.g. is unsnoozed). If the action is still valid and this setting is set to true, then the action will then be fired and repeat/escalate as normal. Otherwise the action will remain unfired until it is invalidated.