WooCommerce - Add Custom Status

functions.php

<?php
/**
 * @snippet       WooCommerce - Add custom status
 * @author        Redlight Media AB / Christopher Hedqvist
 * @compatible    WooCommerce 4.1.1
 */
add_filter('wc_order_statuses', 'add_custom_order_status' );
public function add_custom_order_status( $order_statuses ){
        $order_statuses['wc-fetched'] = __('Fetched');
        return $order_statuses;
}

add_action('init', 'register_custom_order_status');
function register_custom_order_status(){
        register_post_status( 'wc-fetched', array(
            'label'                     =>  __('Fetched'),
            'public'                    => true,
            'exclude_from_search'       => false,
            'show_in_admin_all_list'    => true,
            'show_in_admin_status_list' => true,
            'label_count'               => _n_noop( __('Fetched') .  '<span class="count">(%s)</span>', __('Fetched') .  '<span class="count">(%s)</span>' )
        ) );
}