Hi Pankaj.
Unfortunately BAdI UDM_WL_ITEM_CREATE, UDM_WL_ITEM_DISP could control worlist items.
You have to do enhancement to add fields in Process receivables.
1. Append structure into structure FDM_COLL_INVOICE
2. Add Enhancement at the end of functions FDM_COLL_INVOICES_READ & FDM_COLL_INVOICES_READ_CLOSED
You can get more detail of implementation in blog posting named 'Adding fields in the Item level / Invoice level of the Collection management work list' in this area.