Unable to Set Custom Event action in Agent Step Card/Carousel Buttons

I created a function for a dynamic Card/Carousel. This works within the when Agent Step but the custom event is returned as open url.

I tried to pass a custom event type to my Agent step Card/Carousel Button.
The problem is the built-in card/carousel only sets "type": "open_url" which generates a button that can only takes users away to an external url. I am unable to pass a custom event within the chat environment.

Is there a work around for this behaviour?