I think it is very hard to design a complete and complex Dialog. Happy Paths are easy and I already used the tool Storywriter but it's not a clear way. You always forget an error Path and you never know what crazy stuff a user might say at a point. You are developing and recognize: Oh man, I need to talk to the product owner again, what to do in this special case.
It's very hard to work when developers and product owner are working together on that dialog. It's such a time waist.
I would love to use a Dialog Builder Tool where you can define a happy path, get recommendation for error paths or stuff a user could and get warnings when a Skill has no further flow at a point. The tool should produce a flowchart in a clear way.
Currently it's hard to model a more complex dialog.