When you draw a data flow from one step to the next, the data structure columns in the first step will automatically be created in the second step. You can also manually create data structure columns by using the Add Columns and Add a Row tools on the Data Structure Columns tab of a data input, an action or a data output.
These tools may not be available for actions, such as a data lookup or data split object, which do not modify the structure of the data format.