The default display for a book is all documents in the folder assigned to the book. However, you can display (and therefore choose from) clauses in the parent folder and all clauses in folders beneath the parent folder. Just click the Tree checkbox. The left panel screen will be repainted, adding to the top of the list any sub-folders beneath the parent folder. A sub-folder will be displayed between {curley braces}. Double click on the sub-folder name to display its contents.