Dear All
I am closing this thread, in the relationship tab, the following relationship type needs to be maintained in comm_hierarchy for the category which you need to maintain the accessories.
If CRM is a standalone system then the accessories can be maintained independently for the main product
However if you have ECC as the backend system then you need to download the Bills of Material which is maintained in SAP ECC to SAP CRM, following blog below is very helpful for the same
Bill Of Material Settings in CRM and ECC
Kind Regards
Atul