Well, here is the solution (until MS changes things again) for MS Word 16 on Mac
Main thing to be aware of is endnotes need to be at end of a section, not end of document, which is the default.
1: After last text, but before endnotes. Insert a section break, new page
2: In main menu: . This brings up a dialogue box where you can change where endnotes are placed (who would have guessed that). Choose “end of section” for endnotes, and “apply changes” to “entire document”.
This tells Word to place endnotes at end of the section you have just created … but nothing happens, because the Word default is to place endnotes at end, and you have to tell it to STOP doing that. Again, who would have guessed
3: in main menu: , then “Microsoft word” then “margins” and you will get to a dialogue box where you can modify the section layout (of the sections you have just created). ‘Suppress endnotes’ is on by default. Untick that box.
“Suppress endnotes” is an MS way of saying “no matter what the user says, suppress their thinking, and put all the endnotes at the end of the document”. When you untick this, you will find the endnotes placed immediately AFTER the section break, however, this is what MS means by “end of section”
4: You can now enter text after your endnotes, such as a bibliography – cut and paste it from where your citation manager put it in the document. If you add (say) a numbered heading, then this will get picked up in correct order, and appear in table of contents.
5: go into the footer of the new section, and continue page numbers from previous, otherwise your bibliography will restart at page number 1.
If a future version of Word changes where commands are, which it almost certainly will, the key is to create a section, place endnotes at end of the section, and find somewhere in the layout where you can tell it not to suppress endnotes.