Toolbar.setShowArrow

Sets whether to show an overflow menu when toolbar isn’t allocated enough size to show all of its items. If true, items which can’t fit in toolbar, and which have a proxy menu item set by [gtk.tool_item.ToolItem.setProxyMenuItem] or #GtkToolItem::create-menu-proxy, will be available in an overflow menu, which can be opened by an added arrow button. If false, toolbar will request enough size to fit all of its child items without any overflow.