create a return for an order or order line by reference

 Hi

I am doing a return test case as mentioned in the user guide

User guide
Release 12.1
Part No. E13408-02
Page  117

To create a return for an order or order line by reference:
1. Navigate to the Find Orders window and query a sales order your want to return.
Make sure you are using a Mixed order type.
2. Select the Line Type for the return in the Returns Tab on the Line Items form.

Here I get the following error

"YOu are not allowed to update the order line because: Order line has been closed"

I can create return manually or using copy feature.