Hi,
Do you want your fields in CJ20N like this?
and Do you want your fields in CN41N like this?
If yes, then there are two options. Either you can create an additional tab for all the categories that you have mentioned OR you can put these categories under User Fields as I did.
Option1:-
For this, you need to go to SPRO->Project System->Structures->Operative Structures->Work Breakdown Structures->User Interface Settings->Layout of WBS Element Detail Screens->Define Layout for WBS Element Details Screens.
Now, here you need to put up the tab page and put up the credentials. It would tough for me to explain you the steps of doing this. But, if you have some documentation or go it carefully. You would be able to achieve that.
Option2:-
Either go through SPRO (i.e under User Interface Settings->Create User Defined Fields for WBS Elements) or execute OPS1.
System would ask you to create only 4 text input fields. Enter your categories over there and make sure they are visible through field selection OPUK. (fields would be USR01, USR02, USR03, USR04).
Now, as far as Predefined List Option is concerned. I would rather suggest you to contact your ABAPER and get the field elements for those categores OR you can handle this through Substitutions (OPSI) by making prerequisite as any of the obvious fields like Project Def'n etc and then you could get the your categories being populated through substitution.
I hope this may help you. Else, wait for other experts to guide you on this.
Regards,
Amit