Ameya,
Kindly check the TR to see how the table related object entries (R3TR TABU for table,R3TR FUGR for function group as this table is having TMG,R3TR DOMA for domains,R3TR DTEL for data elements) got saved in the TR.Btw, how the tables related to CIN got created in DEV initially ie manual implementaion of a SAP Note or through SNOTE ?
J_1IWRKCUS entries needs to be maintained in respective systems and can't be transported.If SAP has designed this table to be maintained in respective systems,then let it be in the same way rather than fiddling with the TMG of standard table.
K.Kiran.