Hi SAP,
As i know, your data source base table is BSEG.
So you may don't need any enhancement code here.
You can just add required(please don't use ZZ) field from BSEG to include structure CI_BSIS which part of your structure.
Later uncheck hide and field only known in exit at RSA6 for added field..
After that you can try extraction at RSA3 and let us know the results.
Thanks