Gtk.ButtonBox.prototype.set_child_secondary

function set_child_secondary(child:Gtk.Widget, is_secondary:Boolean):void {
    // Gjs wrapper for gtk_button_box_set_child_secondary()
}

Sets whether child should appear in a secondary group of children. A typical use of a secondary child is the help button in a dialog.

This group appears after the other children if the style is Gtk.ButtonBoxStyle.start, Gtk.ButtonBoxStyle.spread or Gtk.ButtonBoxStyle.edge, and before the other children if the style is Gtk.ButtonBoxStyle.end. For horizontal button boxes, the definition of before/after depends on direction of the widget (see Gtk.set_direction). If the style is Gtk.ButtonBoxStyle.start or Gtk.ButtonBoxStyle.end, then the secondary children are aligned at the other end of the button box from the main children. For the other styles, they appear immediately next to the main children.