When adding links under Appearance > Menus, there should be an option called “Open link in a new window/tab” for each menu item. Please try enabling it.
I apologize for the delayed response. The “Open link in a new window/tab” option should still be available when editing your menu items. I have attached a screenshot below showing where you can find it.
Please follow these steps:
Navigate toAppearance > Menus in your WordPress dashboard.
Click on the Screen Options tab in the top right corner.
Ensure that the Link Target option is checked.
Expand the menu item you want to edit, and you should now see the “Open link in a new window/tab” checkbox available.
If the option still isn’t visible, could you please let us know which theme framework you are using—Unyson or Redux? This will help us provide more specific assistance.