Currently it is only possible to batch upload data via xlsx file. Providing such a file is cumbersome in cases where data is nested (e.g. 1:n relationship between BP and identifiers).
The service would need to extract the external ID based on the mapping related to the target data source, escape characters, strip line breaks and parse the objects into "record", then upsert batches of 1000 records into the target data source via https://developer.cdq.com/reference-docs/data-exchange/V4/tag/Business-Partners/#tag/Business-Partners/paths/~1v4~1storages~1{storageId}~1businesspartners/put