Nav menu elements normally appear on all pages. Do you want to add section links which only appear on the specific page? You can use the “wp_nav_menu” filter to add additional elements. Links to page sections are more typically within their own contents list that are part of the page’s output, separate from the nav menu. Something like that could be managed on the page’s template. You can still style it like a nav menu if you like, content links don’t have to look like a table of contents.
@bcworkz thanks so much for your helpful reply. I do appreciate 🙂