Send custom bill line level attributes from SM to RMCS

Summary: We have a requirement to send the custom attribute UsageQuantity_c at the Subscription bill line level to the Quantity attribute in RMCS. But we are unable to find the service mapping at the bill line level for the same in the SM-RMCS Integration Service Mapping. Is there any possible way to add this in the service mapping or in the algorithm, so that it can be sent to RMCS

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