I didn't want to stomp all over Bill's thread - making buttons for nav bar - mouseOver question (talkgraphics.com) - but I also didn't want Acorn thinking I had ignored him.

The site in question >>> ccsaint-clair.com.au/

You could readily use my page mega-menu approach for your detailed site map. Currently, I have no sense of where I am or going and only when hitting page bottom do I see the Site Map/Index link.
If you make the same Link a Hamburger, sticky top of page, and add the Close icon back link then you will be cooking with gas.

From https://ccsaint-clair.com.au/site-map.html, I am finding a lot of 404s.
It is not clear that some Links are to PDFs, external links or sub-sites, you need an icon for each and any jump externally or to a document needs to open into a new Tab.

Acorn
I fixed up the 404s quick pronto. They broke when I split the site and I have since flailed myself with the horse hair cat-o-nines and sacrificed a chicken on the altar (KFC on a plate)

I didn't want to make a site map more important than the menu, so I added a static hamburger icon to the menu bar instead.
I did, however, add markers to the menu bar to show which page you, as the visitor, are currently viewing.
I added the title and sub heading to each page without a menu bar, again for navigation clarity.
I added icons on the site map to indicate which links are PDF and which shoot off to Amazon. The internal links I left blank. I don't love the aesthetics, but I see the value.
Finally, I added a back icon to the site map that takes you back to the page you were on when you clicked the hamburger icon.

Thank you for the suggestions. The advice I receive on these forums is always appreciated.