pewc_filter_child_products_method.php

<?php
/**
 * Filter which product type is used in the Products field
 * @param	$product_type
 * @param	$product_id			Product ID - use this to conditionally change product type per product
 * @param $field_id				Field ID - use this to conditionally change product type per field
 */
function prefix_search_products( $product_type, $product_id, $field_id ) {
	$product_type = 'woocommerce_json_search_products_and_variations'; // Allows you to include variations
	// $product_type = 'variable_subscriptions'; // Include variations for subscriptions
	return $product_type;
}
add_filter( 'pewc_filter_child_products_method', 'prefix_search_products', 10, 3 );