The citation follows the same rules as previously. In a multiple edition book, it is only the full reference that identifies the edition.
The template below shows how references are constructed.
Author, initial (including multiple authors) … (year of publication) … Title of book. … edition no. … Place published: … Publisher
Marshall, J.E. and Raynor, M.D. (2020) Myles Textbook for Midwives. 17th ed. London: Elsevier.