Use the Filter to show portraits belonging to a specific category. Choose the category name, then the specific category. The portraits belonging to that category will be displayed, excluding all others.
This is useful if you need to reassign a batch of people to a new group to filter - simply filter the group, select all, and reassign the portraits as a batch. In this example, all the portraits in the Group-Jameson have been changed to the Group named Jameson-Davies.
You can also use the filter to find a specific person without scrolling through the entire portrait set, using LName or FName.