Flex UI and Flex WebChat UI API References are now available starting from Flex UI v1.19 and Flex WebChat UI v2.4 here:
These API references describe all available public interfaces, methods and properties. It also includes a full list of registered Actions and their payloads, as well as a list of programmable components.
API references are available as Pilot. The Flex team looks forward to hearing your feedback and making further improvements. To submit feedback, use the feedback widget which you can find on each page of the API Reference.