The add button can only be used in the reference set selector. With this button the end-user can select objects that have to be added to the reference set selector.
This property indicates the form that is shown to end-end user after he clicks on this button. The end-user can use this form to select objects that have to be added to the reference set selector. This form should contain a data grid or template grid connected to the same entity as the reference set selector.
The form settings specify how the form should be opened. See Opening Forms.
See Button Properties.