Call subVI as independent window

VI A is my primary user interface. At the click of a button, it may open a separate window, VI B, which may remain open for an extended period of time and operate independently of A. Now, my question is, what is the best practice for how to call B, without hanging the user interface of A? The software will be built into an app, so I can't use anything involving VI Server.

Just to be clear – I'm not asking how to COMMUNICATE information between the two VI's, but simply how to CALL B in the most straightforward manner. B might get some friends in the future, and I'd rather not create a parallel loop for each if there's a better way.