Order statuses and stock subtraction - need help

Hi. I'm having a problem with product stock when store administrator edits existing order.

I checked Order Status and Processing Order Status in store Settings, but still can't figure out how it should be set up.

When we edit an existing order in OpenCart admin panel, we need that products would not subtract stock if the product is already added to the order we edit.

We use these order statuses:
1. Pending - when administrator adds a new order from admin panel
2. Processing - when any order is paid but not shipped yet.
3. Shipped - when we send the order
4. Complete - when the order is complete.

If product Status is Pending or Processing, we need to be able to edit order (customer details etc.) without system decreasing stock of the products which were already added in the order previously (and avoiding the error message that there is not much stock).

Any guidance how should I setup Order Status and Processing Order Status in this situation?

Thanks!

When you want to edit order and stock has become zero. You can change the order history of the order to Pending.
And this Pending status should not be marked in your "Complete" and "Processing" order statuses in the system settings.

So when you change the status it will reduce the stock. As it would be counted as Negative order status. And then when you edit the error would not come.
You can read this blog how the order status stock reduction works.

Also, check this extension which lets you edit the order without actually changing the order status: Customized one page order entry