Seeing discussion at among others,
https://sourceforge.net/p/windjview/discussion/392867/thread/9cf34db6/
"Where does WinDjView stores it's bookmarks? "
- it appears that unlike a typical pdf file including bookmarks, the outline (or bookmarks) created using WinDjView (Edit / Add Bookmark) are not stored in the subject file but in the Windows registry.
There are outline/bookmark creators such as HandyOutliner v.1.1.6.3, djvu_BookmarkTool-2.0 etc, but for the manual creation of simple bookmarks of limited number in a file and where the desired target location is easily visible in the main screen it would be convenient to emulate the method of Adobe Acrobat Pro which (at least in its older manifestation) allowed creation of a bookmark by e.g. selecting the text in main window, going to bookmarks / options menu and selecting create new bookmark , adjusting as necessary the copied text from main window then confirming OK. After saving the pdf such bookmark(s) would be part of the file itself, be portable and not have a separate existence outside the file.
Currently DjVuLibre DjView itself seems to omit such functionality.
Thanks for the great program btw.