How to Add DFF to Chart of Accounts Value Set

Hi,

A customer I support is using 21D (11.13.21.10.0).

One of their Chart of Accounts Segments (Cost Centre) is called XX_COSTCENTER.

They would like to add a DFF field to the Value Set which would allow them to define an email address against each Cost Centre.

I cannot see if / how that can be done though.

I had a look on CCC before posting here, and found this post:

How to add EFFs/ Attributes to GL Segments, Manager's name on a cost center — oracle-ccc

Where someone was asking:

We have cost center as one of our segments in the GL chart of accounts.