In Boost, and in "custom menu items" I create my items using the "target=blank" ending at the end of the line, like so:
-Rick's Contact Info|https://www.rjerzxxx.com/navbar/contact.html"target="_blank
I am not sure if this will work in your theme, but it is worth a try.
-Rick's Contact Info|https://www.rjerzxxx.com/navbar/contact.html"target="_blank
I am not sure if this will work in your theme, but it is worth a try.