How can I hide a page from the menu, but still have it accessible through a link?

This article shows you how to have a page accessible by Google or direct link, but not have it visible in the website menu.

Start by editing the the page settings, right-clicking the page title in the page tree, and selecting Edit.

Go to the 'Access' tab, where you will find the option 'Page enabled in menus', and turn it off so that it is no longer green (On older versions it is a checkbox). Don't forget to save.