(Ugh... I had a much nicer writeup but I accientally closed the tab I was working in. :( )

I noticed that the GTK Save Dialog has an Alt-B shortcut for expanding the Browse for other folders entry.

I suggest that upon expanding that with the shortcut the focus goes to the folder selector so that one can start typing the name of the folder and/or use the arrow keys without further action.

This would be very convenient and be more intuitive, because if a user expands that dialog, the next thing he intends to do is very likely to be use the folder selector.