Ingredients, Courses, and Nationalities are arranged into Categories. For example, the Nationality "Italian" is also a Category which includes both “Sicilian” and “Tuscan.” 

If you want to change how Categories are arranged, go to the Edit Dictionary... submenu of the Edit menu and select either Ingredients, Courses, or Nationalities. You'll then be able to change Categories (among other things) to your heart's content. The details are under Editing the Dictionary under the Editing Help topic.