Admin Toolbar Menu Generator

<?php
/**
 * The "My Plugin" toolbar menu.
 */

/**
 * Resolves a menu link.
 *
 * An absolute URL is used as written; anything else is treated as a path
 * inside wp-admin, which is what a settings page link is.
 *
 * @param string $link URL or admin path.
 * @return string
 */
function my_plugin_admin_bar_url( $link ) {
	return preg_match( '#^https?://#', $link ) ? $link : admin_url( $link );
}

/**
 * Adds the node and its submenu.
 *
 * @param WP_Admin_Bar $wp_admin_bar The toolbar.
 */
function my_plugin_admin_bar( $wp_admin_bar ) {
	if ( ! current_user_can( 'manage_options' ) ) {
		return;
	}

	$wp_admin_bar->add_node(
		array(
			'id'    => 'my_plugin_tools',
			// The icon is markup, so the title is escaped before it goes in.
			'title' => '<span class="ab-icon dashicons-admin-generic" aria-hidden="true"></span>'
				. '<span class="ab-label">' . esc_html__( 'My Plugin', 'my-plugin' ) . '</span>',
			// No href: the node opens its submenu instead of going anywhere.
			'href'  => false,
			'meta'  => array(
				'title' => esc_attr__( 'My Plugin', 'my-plugin' ),
			),
		)
	);

	$wp_admin_bar->add_node(
		array(
			'id'     => 'my_plugin_settings',
			'parent' => 'my_plugin_tools',
			'title'  => esc_html__( 'Settings', 'my-plugin' ),
			'href'   => my_plugin_admin_bar_url( 'options-general.php?page=my-plugin' ),
		)
	);

	$wp_admin_bar->add_node(
		array(
			'id'     => 'my_plugin_docs',
			'parent' => 'my_plugin_tools',
			'title'  => esc_html__( 'Documentation', 'my-plugin' ),
			'href'   => my_plugin_admin_bar_url( 'https://example.com/docs/' ),
		)
	);
}
add_action( 'admin_bar_menu', 'my_plugin_admin_bar', 100 );