Is there any hierarchy in intents such as high level intent and low level intent for example intent: event(high or parent) intent:host_event(low or child) intent:attend_event(low or child)

I don’t believe there’s currently a way to do this in Rasa, although there is something similar for entities: Composite entities support · Issue #316 · RasaHQ/rasa · GitHub

We have something called Retrieval Intents but I’m not sure if that’s what you’re looking for. There’s a blog post on this.