Add custom fields to both single and archive pages in WooCommerce https://wpsites.net/wordpress-tutorials/sub-heading-on-single-shop-page-archives-in-woocommerce/

woocommerce-sub-heading.php

add_action('woocommerce_product_options_general_product_data', 'custom_woocommerce_product_fields');
function custom_woocommerce_product_fields() {
    woocommerce_wp_text_input([
        'id' => '_custom_field',
        'label' => __('Custom Field', 'woocommerce'),
        'desc_tip' => 'true',
        'description' => __('Enter the value for the custom field.', 'woocommerce'),
    ]);
}

add_action('woocommerce_process_product_meta', 'save_custom_woocommerce_product_fields');
function save_custom_woocommerce_product_fields($post_id) {
    $custom_field_value = isset($_POST['_custom_field']) ? sanitize_text_field($_POST['_custom_field']) : '';
    update_post_meta($post_id, '_custom_field', $custom_field_value);
}

add_action('woocommerce_single_product_summary', 'display_custom_field_single_product', 25);
function display_custom_field_single_product() {
    global $product;
    $custom_field_value = get_post_meta($product->get_id(), '_custom_field', true);
    if ($custom_field_value) {
        echo '<p class="custom-field">' . esc_html($custom_field_value) . '</p>';
    }
}

add_action('woocommerce_after_shop_loop_item_title', 'display_custom_field_archive_page', 15);
function display_custom_field_archive_page() {
    global $product;
    $custom_field_value = get_post_meta($product->get_id(), '_custom_field', true);
    if ($custom_field_value) {
        echo '<p class="custom-field">' . esc_html($custom_field_value) . '</p>';
    }
}