How to update existing DFF setup from "Default Context field value" to "user defined context field v

 Hello,
We want to update the standard DFF in the Transaction Form from "Default Context field value" to "user defined context field value".
(Application = Receivables, Title = Transaction Information)

Currently, we have defined attributes under the 'Global Data Elements' context field values and have many transactions entered that way.
But we realized that the functionality "Copy Transaction information Flexfield to Credit Memo" does not work because we were told our DFF is not setup as user defined context field value.

Please advise on the proper way to update our DFF setup now.

Thanks !
Servane