How to use advance link attributes in WordPress menu
1. Expand the Screen Options
On your Appearance > Menus page, click the ‘Screen Options’ link in the top right corner.
2. Enable the ‘Link Target’ option
Within the Screen Options page you will see a ‘Link Target’ checkbox. Enable this option and close the screen options.
3: Enable the ‘Open link in a new tab’ option for a menu item
Expand the options for a menu ite m (click the small down arrow to the right of the menu item).
Within the menu options you should see a new ‘Open link in a new tab’ option. Enable this and click the ‘Save Menu’ button.