That option is not present and is unlikely to be implemented. You can already arrange the books in a calibre quite a few different ways. Personally, with a library over 15,000 books, there is no way that I would consider being able to drag the books into a random order to be useful.
That question has been asked many times over more than a decade. See
Rearranging order of books stored in Calibre for an example from 2012.