This screenshot of a rule set's layout editor shows the Fields palette and a list of the layout's fields in the center pane.
In this image, one of the items in the Fields palette is a polymorphic object (ExpenseDff), and it is expanded in the palette to show the list of the object's sub-fields.
The center pane contains the following fields.
The polymorphic object's @all field is listed under the object in the center pane.