I am unaware of any means to do such a thing. I have an application where that was needed and I generated link code for the sidebar navemenu in a third party application and posted there in a text widget. Worked great but a lot of work to do all the time.
I have the thing where external links open in a new window running - this also operates in the nav bar. From a usability point of view, opening in a new window is an unexpected behavior so you might want to re-consider.