1. Click 
on the Toolbar;
Or, go to Run --> Preview node type from the top menu.
2. Select a node type format in the appeared form:
eXo: the standard XML content type to be used with XML-formatted node type streams.
CND: the experimental content type for the compact node type definition files.
3. Click Generate. The generated node type definition will be displayed in the separate tab of Operation pane with title Preview node type:
