You deactivated a value of an extension field of type list, however this value already has been used on old documents and only code is displayed instead description/value.
SAP Cloud for Customer.
Currently this is the system expected behavior, once you deactivate the code value, it is getting removed from the metadata there will be no description available anymore hence the UI shows the
code content. So the meaning of deactivated code is that it is not valid anymore.
If you want to remove it temporarily - e.g. dependent on a business role - as an alternative you can use code list restriction where the value will no longer be available for selection, however still available on already used documents.
Code, extension field list, list value. , KBA , AP-RC-UIF-FLX , Page Layout & Key User Configuration , How To