How To Create a Progress Window in IB Storyboard?

I have an older MacOS app where in IB (no storyboards) I created a main window/view and a progress window/view in one xib in response to a menu item. In a new MacOS app (using much of the code from the older menu item code), in IB storyboard I have a window controller/window/view/subviews in the storyboard, but I cannot seem to find a way to also include in the storyboard a progress panel (to hook up to an outlet in the view controller).

I can create the same window/panel/progress bar that I had in the older app in a separate xib. So I suppose (in objective c) I can just load the xib???

So, is there a better way to implement a separate progress window(s) in a storyboard and hook them up to outlets? I think I'm missing something

And what happened to NSPanels?