void insert(GtkToolItem item, int pos);

Inserts a widget that is subclass of GtkToolItem to the toolbar at a certain position.

If pos is 0, it is prepended at the beginning of the toolbar, before all items. If pos is negative, it is appended after all other elements.

Despite all the other prepend_*, append_* or insert_* methods, this one here is the only valid. The other ones are all deprecated.