You may find yourself searching for menu items to add that simply do not appear on the “Menus” page. This is due to the fact that WordPress will not automatically show all taxonomies (types, tags, categories, regions) by default. If you find yourself unable to find a certain item, simply:
- Visit “Appearance > Menus” in your WordPress Dashboard.
- On the top right of the screen click “Screen Options“.
- Check any additional types of content you wish to be able to add to your menu.
- Screen Options (WordPress.org Codex)