I am trying to sort by expression in a pivot table and I'm having some issues. I've received the output I'm looking for, but I want to sort by another criteria, a numerical index for each title, say Batman = 1, Detective Comics = 2, Fantastic Four = 3, which is not part of the pivot table and I don't want to display it. I've been told to use 'sort by expression' but I'm not sure how to proceed.