Add field for any arbitrary URL for the Menu schema for their Business profile. This only works with the main location.

menu-schema-url-for-bp.php

<?php
/**
 * Plugin Name: Menu Schema URL for Business Profile
 * Plugin URI: http://themeofthecrop.com
 * Description: Add field for any arbitrary URL for the Menu schema for their Business profile. This only works with the main location.
 * Version: 0.0.1
 * Author: Theme of the Crop
 * Author URI: http://themeofthecrop.com
 * License:     GNU General Public License v2.0 or later
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU
 * General Public License as published by the Free Software Foundation; either version 2 of the License,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write
 * to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */
defined( 'ABSPATH' ) || exit;

/**
 * Add an option to enter a menu URL in Business Profile settings
 *
 * @param sapLibrary $sap Simple Admin Pages library instance
 * @since 1.5
 */
function msrfbp_add_menu_setting( $sap ) {

	$sap->add_setting(
		'bpfwp-settings',
		'bpfwp-contact',
		'text',
		array(
			'id'           => 'menu-url',
			'title'        => __( 'Menu URL', 'business-profile' ),
			'description'  => __( 'Enter a direct URL (including http://) to the main restaurant menu on your website. Entering a URL will override the Menu option selected above.', 'business-profile' ),
			'placeholder'  => 'http://',
		)
	);

	return $sap;
}
add_filter( 'bpfwp_settings_page', 'msrfbp_add_menu_setting' );

/**
 * Register the menu component in the Business Profile contact card
 *
 * @param array $components List component callback functions to print details
 * @since 1.5
 */
function msrfbp_add_menu_callback( $components ) {
	$components['menu'] = 'msrfbp_print_menu_schema';
	return $components;
}
add_filter( 'bpwfwp_component_callbacks', 'msrfbp_add_menu_callback' );

/**
 * Print the menu schema details in the Business Profile contact card
 *
 * @param int $location A post ID if this is for a specific location
 * @since 1.5
 */
function msrfbp_print_menu_schema( $location = false ) {

	$menu_url = bpfwp_setting( 'menu-url', $location );
	if ( empty( $menu_url ) ) {
		return;
	}
	?>

	<meta itemprop="menu" itemtype="http://schema.org/menu" content="<?php echo esc_url( $menu_url ); ?>">

	<?php
}