Thanks Konstantin.
I did it in other way. I created a sub object and set that as a delegation. I then redefined the WI text. Which at last worked. I still have a query related to this. When I was doing hit & trial of updating the WI text in PFTC and then executing the Transaction Code SWU_OBUF.The WI was not coming in the NWBC--> Work Overview immediately. This got visible after 2-3 hrs. Is it because of any background job ?
Thanks for giving this list of tables but is this the complete list of IBO* tables which needs to have relevant entries for the Custom task.