How can I get the dropdown Nav bar stay open across pages?

My client has this to say about my nav bar:
“Just a quick thing we’ve noticed: when you click on one of the items under one of the sections ie. Introduction in Section 1, you are taken to that part of the document but the navigation on the left hand side closes up again. Is it meant to be like that? Doesn’t feel right…”

What can I do to make the nav bar section stay open until another section is opened, making the first section close? It should also ideally stay open when loading across pages from the same section.

Any help appreciated, thanks!

Here is my public share link: Webflow - Creative Estuary Cultural Toolkit