While the items column in the staff client is sortable, the same is not true for the cart view in the OPAC. I know that the most we could do is sort on the first callnumber available in the list, but I think this would still be helpful in some setups. For example for libraries with only one branch it would be really helpful if the column was sortable as it would help to generate a list that can be used at the library to efficiently get the books from the shelves.
I just ran into this again looking through old tickets - the item display in the staff interface is really useful, it would be nice if the OPAC could be adapted to be the same or more similar (including sorting!)