It’s suggested in GNOME bug 82567 that Metacity could allow a left-click on the titlebar to launch a menu which allowed the user to navigate to the parent, grandparent, or further ancestor of the window. This would only make sense where the window could represent a container which itself was contained in some other container hierarchically (which amounts to the file manager, pretty much).
This would require a new window hint in order to work. It would replicate behaviour that is generally the province of toolbars and appears to have WONTFIX written all over it.
This is similar to a more useful and general recent suggestion that windows should be able to add a draggable icon in the titlebar, as is done on OS X. Your chronicler would like to see this done, but is aware that the obstacles between there and here are formidable.
Photo of Jackson the dog © ItsGreg, cc-by-nd.