By “hamburger menu” are you referring to the sidebar? Usually “hamburger menu” refers to the menu on mobile only, but since this sidebar is also displayed with a hamburger icon, maybe this is what you’re talking about.
If so, perhaps this has changed since this original post in 2021. It appears that I can remove these pages from the overflow menu. People could still navigate directly to them with the link, but they wouldn’t show up here.
Please correct me if I got this wrong!