salesforce writeback batch append question

I have a dataset that has data flowing in batches and every batch group ( has a unique group name (column) , I want to writeback this data as it comes after necessary transformations to the same writeback connector to append only unprocessed records.

While trying to do this, I get " it is illegal to have 2 inputs where only 1 is needed"

How can I make this possible with one single input dataset with different group filters attaching to one single Salesforce writeback dataset to append only new records from batches?