Protecting Custom Links in menus

Is there any way to protect a menu item that is a “Custom Link”. Even if I take a normally protected screen and add it to the menu as a custom link (rather than via Pages), it is not protected.

My meager goal was to create some sub-menus that used #anchors to target particular places on a protected page. But the menu item then becomes visible regardless of security setting.

https://www.ads-software.com/plugins/contexture-page-security/