"I highly recommend"
— Michael Dexter What They Say

Why can’t I add a certain link to the menu?

In AppearanceMenus, you can select Pages, Posts, Sermons, Links, etc. to add to your menu. If the option you are looking for is not showing, click on Screen Options at the top right to make it show on the menus screen.

The “Links” option will let you enter the URL to any page on your site or another.

Menu Screen Options