When a mapping group is applied to a column in a pipeline, the contents of the column are transformed inline. In order to see the unmapped and mapped values at the same time, you'll need to add a data lineage column.
To do this, you must add a Copy Column transformation that makes a copy of the Mapping Group column -- but this be done before adding the Mapping Group transformation. The name of the copied column can be the same as the column from which it is copied, but we recommend adding an identifying prefix of some sort (such as "src_" or "dl_").
