Head stage: Mapping output
On the Output tab, select Edit in the Columns section. Here, you can specify how the output columns are derived, that is, what input columns map onto them or how they are generated.
The drop-down shows the input or generated columns. These are read only and cannot be modified on this tab.
The Maps from column input column section that appears when you click Edit in the columns section allows you to specify the relationship between the columns being input to the Head stage and the output columns.