You can add function modules and modify existing function modules in the Modification Assistant. You can:
During preliminary corrections, the name of the function module added can also come from the SAP namespace.
Create the module and assign it to an existing function group. Define the function module interface by determining its parameters and exceptions. Then write the function module’s code. At this point, the pushbuttons that you are accustomed to using in the ABAP Editor are put at your disposal. For further information, see
Be certain that this type of change is compatible with your parameters and the contents of the function module.
You can add new parameters. If you do not enter a Default for newly added parameters, they automatically receive the attribute Optional.
You can always change the reference fields and defaults of those parameters that already exist.
The procdure for modifying function module code is much the same as the procedure for modifying programs.
Use Modification overview to display an overview of the modifications you have made to the module.