current way to switch tabs (subdialogs) in a tabbed dialog is not intuitive / hard to use: one has to focus somehow on the tab's title, then use arrows to switch. a single shortcut (actualy 2: forward and backward) would do better.
This is a GTK behavior; not something we can control. If you want to suggest improvements to GTK, you can use gnome's bugzilla (bugzilla.gnome.org) or the gtk development list.
Moving invalid bugs to the /dev/null product.