Use this snippet to enable the toggle-box Component view when using the Stacked layout only.

woocommerce-composites-toggle-box-stacked.php

<?php
/**
 * Plugin Name: WooCommerce Composite Products - Enable the toggle-box Component view with the Stacked layout
 * Plugin URI: https://woocommerce.com/products/composite-products/
 * Description: Use this snippet to enable the toggle-box Component view when using the Stacked layout only.
 * Version: 1.0
 * Author: SomewhereWarm
 * Author URI: https://somewherewarm.gr/
 * Developer: Manos Psychogyiopoulos
 *
 * Requires at least: 3.8
 * Tested up to: 5.3
 *
 * Copyright: © 2017-2020 SomewhereWarm SMPC ([email protected]).
 * License: GNU General Public License v3.0
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */
 
// To use this snippet, download this file into your plugins directory and activate it, or copy the code under this line into the functions.php file of your (child) theme.
 
add_filter( 'woocommerce_composite_component_toggled', 'wc_cp_component_toggled', 10, 3 );

function wc_cp_component_toggled( $toggled, $component_id, $composite ) {
	$style = $composite->get_composite_layout_style();
	return $style === 'single';
}