Various sorting options are available until you have 100 titles in your Borrowing History. After you have more than 100 titles, the information is no longer stored in the same way, because keeping all of that information in the system would cause page load times to be unacceptably slow.
Adding titles to your Completed shelf allows you to sort and filter with more flexibility. In addition to sorting, you can exclude titles you don't want, and filter the shelf, making it easier to find a specific title.
