In the interests of DO12 perfection. (This came up when I was systematically saving a number of earlier layouts in DO12 so that the new DPI magic could work.)
Suppose that I have a layout Bunny\Rabbit, that is, the layout Rabbit is in the folder Bunny. I open the layout, make a small change in the layout, and then press the Prefs LayoutSave=single button, intending to save the new version over the top of the old version.
On the model of earlier DO versions, what should appear as the default in the resulting dialogue box is Bunny/Rabbit, so that I can easily save the new layout over the top of the old one. What actually appears is just Rabbit, so that unless I fiddle about, I end up saving a second version of the layout in the 'root' layout folder rather than overwriting the old one.