Hi there,
1. Edit your page and select a Block where you want the link to jump to.
1.1 With that block selected go to the Advanced tab, in the HTML Anchor field add your anchor name eg. halfway-down
2. In Appearance > Menus add a Custom Link, give it a label and in the URL field add: #halfway-down
2.1 Note the URL is the HTML Anchor proceeded by a #
So now this assumes that all pages have a halfway-down anchor on them. Or the menu item won’t work.
If you want the menu item to always jump to a specific page and halfway down then the URL of your menu item would be:
https://yourdomain.com/your-page/#halfway-down
and for the home page it would be:
https://yourdomain.com/#halfway-down
Does that help ?