You can add menu items above and below Header element by placing custom menu blocks in 'HeaderAbove' and 'HeaderBelow' Widget Areas from WordPress backend.Go to WordPress dashboard -> Appearance -> Widget -> drag and drop Custom Menu block in HAWidgetArea00/HAWidgetArea01/HAWidgetArea02/HAWidgetArea03 (to place menu above header) and HBWidgetArea00/HBWidgetArea01/HBWidgetArea02/HBWidgetArea03 (to place menu below header)