When you add related controls to a window, you must first add the related object itself, indicated by in the Attributes tree. This will appear on the window as a drop-down list, enabling you to select the required related object. You can then add further attributes from the related object to the window.
To add related controls to a window:
Open the required window, and expand the Attributes tree.
Display only Relationships, then click the relevant relationship.
Click the Window Editor. The control appears on the window.
Expand the relationship in the tree, then add the required related attributes to the window.