federated-wordpress-customizations/woocommerce/processing_to_complete_order.php

<?php

if( ! defined( 'ABSPATH' ) ){
    exit; // Exit if accessed directly.
}

add_action('woocommerce_payment_complete', 'federated_set_new_order_to_complete');

function federated_set_new_order_to_complete($order_id)
{
    $order = wc_get_order($order_id);
    
    if($order->has_status('processing')){
        $order->update_status('completed');
    }
}