Domain Punch Professional allows you to categorize domains into various groups or categories. By default it also includes a number of pre-created domain groups. These groups are displayed in a tree format in the domain category pane.
You can use the Manager > Views > Categories ribbon option to toggle the domain category tree on or off.
To add additional groups to the Manually Grouped List within the domain tree simply right click on the tree and use the Add New Category menu option. See the screen shot below.
To add domains to a group you should right click on a domain name in the main list and select Categorize Selection. Highlight multiple domains (using the ctrl or shift key along with mouse click) and then use the Categorize Selection option to group multiple domains.

Domain categories can be renamed by clicking on the name of the category twice (once to select the category and then a second time to start the in-place editing. Don't double click!)