I’m using Scrivener 3.0 (yay!)
I close the binder and try to use the Next/Previous Documents control in the Header Bar to navigate up and down the binder structure. (As per Section 8.1.1 Header Bar in the manual.)
But clicking on Next or Previous Document opens the Binder!
My assumption is this is a bug, because it seems the point of these controls is to enable Binder navigation without having the Binder open.