Portrait Dialogue - how do you use the Control Group functionality in PD and HQ

The 'Use Control group' checkbox in HQ doesn't do anything, and it has been removed in the more recent versions of the HQ. 

The Control Group in Portrait Dialogue (PD) is just a label, it has no extra functionality. 

You have to first decide how you want to use the Control Group, then copy those control participants into the group of type 'Control Group'. 
The 'Control Group' group type was created for you as a way to organize your work, since it is a common practice.
What you do with them after that is up to how you design the Dialog. 

For example, you may wish to keep 10% of the participants in the Control Group so that they are not processed in order to test if the Campaign results in a positive or negative effect compared to the participants in the Control Group.
UPDATED:  March 24, 2017