FI Validation and Substitution (GGB0 and GGB1) in S/4 Hana system

Hello SAP Gurus,

I need to know how is working the process of Validation and Substitution on the S/4 Hana system.

In our actual SAP ERP we use the standard transaction

GGB0 and OB28---------> Validation.

GGB1 and OBBH--------->Substitution.

and then for a lot of them we have implemented user exit where we have written our z-code.

How look like in S/4 Hana this process? Will be always possible to user the transaction above and will always possible to implement a kind of user exit behind?

I tried to search a bit in Internet, I found some information under this link:

https://help.sap.com/viewer/4ebf1502064b406c964b0911adfb3f01/2020.000/en-US/5c8c2825535f4e3aa9b7f716a0085221.html

But here is mentioning the App on Fiori, my question is more on S/4 HANA GUI. Do you know any official documentation or any information about that?

Thank you in advance.