So my understanding: we do not need to define intent in nlu, if that intent is passed as-is via another medium or typed directly. Rasa does not complain if the intent is not created with training data, as long as it is in the domain file.
@ashek1520 yeps correct, if you mention intent: trigger_response_selector in domain.yml and in nlu.yml you not mentioned this intent with example, you are just fine. This is how payload work but on the other hand if for example you have payload button yes or no intent and you also want that user type the yes or no, for this example you need to define the examples and intent in nlu.yml. I hope this will help you.