This feature is useful when you need to compare an old audiogram with a new one.
Open a measurement window.
To the left of the Measurement screen the Test Type panel will be shown and a new test can be added:
Click Add measurement and select the same Test Type you are going to use, for example HTL.
This item will appear on the panel marked as (2). Now you can run test type HTL and HTL (2) in the same windows.
The second test type can be added after the client already has the measurement completed.