Problem in Extending Customer Business Object with Custom Node with [1,n] cardinality

Hi Cloud Experts Need Help,

I have a scenario to replicate customer payment cards details from SAP ERP to C4C and save it in a node which having [1,n] cardinality,

When i tried to extend the customer business object with node[1,n] m getting error like not extendable as displayed in below screen shot.

So is there any other process or way through which we can extend the standard business object with node[1,n] cardinality?

kindly guide me to solve this issue.

Thanks,

Siraj.