You can only return items in an order if:
They've been fulfilled
They've not already been returned
How do I return an order?
In the admin area
Go to Commerce > Orders.
Next to the order, click View.
Under More, click Return. This option will only appear if the order is returnable.
Chose the Items to return by changing the Quantity next to each item.
Optionally change the Date of the return.
Optionally enter a Reason for return.
Do items get restocked when returning an order?
When returning an order, we automatically restock any products. We ensure things aren't overstocked.
If you want to let the customer keep the item or the item is damaged, then you'll need to do a manual stock adjustment after returning the item.
You need to manually delete any linked items that were created as part of the order (e.g. tickets, memberships, gift vouchers).