When working with custom fields and specially legacy fields in SAP S/4HANA, there is a transaction to use it is called SAP GUI Transaction SCFD_EUI. I would like to share with you that our development team has put together a nice technical document that explains and answer most of the common questions and as well explain the usage of SAP GUI Transaction SCFD_EUI. To find all the details about it, please refer to our WIKI document: Handling of Legacy Fields in SAP S/4HANA
Tank you Ali for sharing.
This is critical information, that I assume 99,99% of all new S/4 projects are not aware about it.
I think it will take years, until project managers and developers will get this together and start using the extension framework actively also for legacy custom fields.
You are very welcome!!!