add_filter( 'manage_edit-shop_order_columns', 'add_payment_method_custom_column', 20 );
    function add_payment_method_custom_column( $columns ) {
     $new_columns = array();
     foreach ( $columns as $column_name => $column_info ) {
     $new_columns[ $column_name ] = $column_info;
     if ( 'order_total' === $column_name ) {
     $new_columns['order_payment'] = __( 'Payment Method', 'my-textdomain' );
     }
     }
     return $new_columns;
    }
    add_action( 'manage_shop_order_posts_custom_column', 'add_payment_method_custom_column_content' );
    function add_payment_method_custom_column_content( $column ) {
     global $post;
     if ( 'order_payment' === $column ) {
     $order = wc_get_order( $post->ID );
     echo $order->payment_method_title;
     }
    }