In InDesign 19.4 on macOS 14.4.1, the document.epubExportPreferences.epubCreatePageNavigation and book.epubExportPreferences.epubCreatePageNavigation properties are supposed to allow scripts to toggle the reflowable EPUB "page navigation" option on and off. However, only the document.epubExportPreferences.epubCreatePageNavigation property functions properly. The book.epubExportPreferences.epubCreatePageNavigation doesn't do anything. Regardless of whether it is "true" or "false", the output always includes the page break markers when outputting reflowable ePub from a book file via scripting.