The Styles.User Styles Section contains the list of User Styles. User Styles are shown in a list, and the list expands to fill the right-hand pane of the main window. Buttons to manipulate the list are beneath the list, including: Add, Edit, and Delete. The arrow items do not apply to User Styles.
You may add User Styles to apply styles to the site that are not possible via the Style Section subsections.
See the User Style help page for more information.