Any data that you want to export must be defined as a dimension within the profile.
If the dimension does not already exist in the profile, you must create it. You can create dimensions using any of the following methods:
Add a dimension to the Transformation.cfg file. See the Dataset Configuration Guide.
Create a new .dim file. See Creating and Editing Derived Dimensions.
Exporting a field of data such as Tracking ID or Email Address (which can have lots of elements) requires that you create a denormal dimension that stores the raw strings of data.
For more information about denormal dimensions, see the Dataset Configuration Guide.