http://codex.wordpress.org/Function_Reference/get_nodes#Display_all_Node_ID.27s_of_the_Current_Page_in_the_Toolbar

WordPress Admin : Display all Node ID's of the Current Page in the Toolbar

// use 'wp_before_admin_bar_render' hook to also get nodes produced by plugins.
add_action( 'wp_before_admin_bar_render', 'add_all_node_ids_to_toolbar' );

function add_all_node_ids_to_toolbar() {

  global $wp_admin_bar;
	$all_toolbar_nodes = $wp_admin_bar->get_nodes();

	if ( $all_toolbar_nodes ) {

		// add a top-level Toolbar item called "Node Id's" to the Toolbar
		$args = array(
			'id'    => 'node_ids',
			'title' => 'Node ID\'s'
		);
		$wp_admin_bar->add_node( $args );

		// add all current parent node id's to the top-level node.
		foreach ( $all_toolbar_nodes as $node  ) {
			if ( isset($node->parent) && $node->parent ) {

				$args = array(
					'id'     => 'node_id_'.$node->id, // prefix id with "node_id_" to make it a unique id
					'title'  => $node->id,
					'parent' => 'node_ids'
					// 'href' => $node->href,
				);
				// add parent node to node "node_ids"
				$wp_admin_bar->add_node($args);
			}
		}

		// add all current Toolbar items to their parent node or to the top-level node
		foreach ( $all_toolbar_nodes as $node ) {

			$args = array(
				'id'      => 'node_id_'.$node->id, // prefix id with "node_id_" to make it a unique id
				'title'   => $node->id,
				// 'href' => $node->href,
			);

			if ( isset($node->parent) && $node->parent ) {
				$args['parent'] = 'node_id_'.$node->parent;
			} else {
				$args['parent'] = 'node_ids';
			}

			$wp_admin_bar->add_node($args);
		}
	}
}