[Adoby]

The easiest way is perhaps to treat the books as parts in a series. Calibre has good support for that. Then the series is the name of the encyclopedia, the book titles are the subtitles and the series number gives the order.

And add BISL as a prefix to the titles and EB, Inc as author. Then the books will appear together.

You can right-click a book and manually edit the metadata. Calibre will then change how the book is sorted.

You could also consider having a separate library for large references. Either separate calibre libraries or virtual libraries. You could even have a separate virtual library for each multivolume work. You can add tabbed access to virtual libraries, so by clicking on a tab all the references are listed.

But you might also consider how you use these books. It is not certain that calibre is the best reader software, especially not if you have the books as PDFs. You could for instance create a master PDF that contains links to all your reference books.