If a class has more than one superclass, you can use the Superclasses Pane to jump from one superclass to another in the Class Relationship Pane.
Note: If you cannot see the Superclasses Pane, your window may be too small. You can see the pane by enlarging your window or by dragging the slider bar at the bottom of the Class Relationship Pane. See Working With a Small Window for more information.
To jump to another superclass:
In the illustration below, if you clicked on Person in the Superclasses pane, the highlight in the Class Relationship pane would jump to the copy of Columnist under Person. If the Person hierarchy was not currently expanded, it would expand to display the Columnist class.
Next: Removing a Superclass