By default, a WordPress menu item open in the same tab. If you want to open it in a new tab or window, right-click on the link and choose the appropriate option from the browser menu.
But it will be better to configure your menu links from the website settings. So a menu item will automatically open in a new tab when a user clicks on it. In WordPress, you can easily do it with a simple trick.
Visit Appearance and from there, Menus to configure your navigation links.
Tap Screen Options from the right top side to see hidden page settings.
Check Link target box. Tap Screen Options again to hide pop down box.
Scroll down to bottom and open any menu items to customize.
Now you have a new checkbox under the Navigation label, Open link in a new tab. Put a tick mark there. Tap up arrow on the right top of the box to close. Repeat this step for all menu items and Save Menu.
That’s all. The readers can open your menu links in a new tab without any external tool support. If you want to customize the menu items again, know How to Add Image Icons to Navigation Menu in WordPress.