Extension
Select Extension to extend an existing part (class) in an application or subapplication. 
Preconditions 
To extend a class, the following conditions must exist: 
•You must be a group member of the application or subapplication. 
•The application or subapplication must be an edition, not a version. 
•The class you want to extend must be visible to the application or subapplication. To be visible, the class must exist in a prerequisite application or, if you are adding the extension to a subapplication, in the containing application. 
Selecting Extension opens a window that prompts you for the name of the class to extend. You can type in the name of the class or, for a list of visible classes, keep the default asterisk (*). After you specify the class to extend, select OK. 
Last modified date: 03/28/2020