Updating Action Tags in GHR/LTM via IPA

unknown

I have created a custom flow for the Terminate action in GHR and am using the standard Terminate action to trigger this custom flow (Term Pending action) and an Employee update within the flow after the Term Pending approval/update to act as the Term Final action. It isn't adding the HRTerminate action tag (to the Term Pending or Term Final action) like the standard flow does. I need it on the Employee update and have tried passing it with the other action fields (Employee_action_tags="HRTerminate"), but that isn't working. Is there some special syntax for updating the action_tags field? Or is it possible to update it at all? Any idea how it is being assigned to the standard flow?

Thanks for any insight!
Katie