The current (fixed) behavior of a GtkNotebook is to display arrows when the
number of tabs can no longer be displayed all at once. When this happens,
it's quite hard to navigate back and forth through the tabs. A better
solution would be to stack the tabs on top of each other so they're always
visible. IIRC, Java/Swing has a property for their JTabbedPane for
precisely this purpose. I would argue for same kind of property for
GtkNotebook.

An argument against this might be that when this happens (too many tabs)
that you should use a different way to display the content, but this is
often not an option (think editors like gedit for example).