UI Connectors and Extensions were released in build 8.0.1053 and have been available since then.
UI Connectors allow a developer with knowledge of a custom control to build a translator for Pega Robotics to interface with. This is only necessary when the control is not supported by Pega Robotics. Building a UI Connector requires knowledge of the methods used within the custom control.
Extensions can be used to add functionality to a supported control. You can enable functionality that is not mapped to Pega Robotics or extend the functionality available.