How can I set the isCompleted status of an order from within a custom module? The default behaviour for commerce is to mark the isCompleted flag on an order to true once the order has been paid for.

I have need to alter this behaviour and only want to mark an order as Complete via manual intervention of a site admin - or after a predefined date has passed.

Is it possible to set the isCompleted flag from within a custom module? 
Right now, I'm listening to the EVENT_AFTER_ORDER_PAID then attempting to set the isCompleted flag and save the order.

What I can't figure out is how to save the order!

Code so far, for what it's worth:

Event::on(
            Order::class, 
            Order::EVENT_AFTER_ORDER_PAID, 
            function(Event $e) {
                $order = $e-&gt;sender;

                $order-&gt;isCompleted = false; // no idea if this is correct

                $order-&gt;saveOrder(); // this doesn't work
            }
        );
This can be achieved with

Event::on(
            Order::class, 
            Order::EVENT_AFTER_COMPLETE_ORDER, 
            function(Event $e) {

                $order = $e-&gt;sender;

                $order-&gt;isCompleted = false;
                Craft::$app-&gt;getElements()-&gt;saveElement($order, false);

            }
        );


But I'm not sure it's actually a good idea anyway.