Groups are new to the discussion. They actually don't become anything in the generated header files, they're just a convenience to help you work with your class model. To create a new group you right click and select "Create Group."

In this case I've created a Birds group to group together my bird classes. All this really does is provide a visual box around my classes. It doesn't restrict how classes can interact or what you can do to individual classes. It does give you a nice way to move a bunch of related classes around the model canvas. It also gives you a nice place to document grouped classes.

If you double click on the group title bar you'll get a dialog box where you can enter group documentation. You can also change the background colour of your groups by selecting the Background Colour button.

You can add classes to your group by right clicking inside the group and creating a new class. You can also drag classes in and out of your group.

WARNING: Due to a frustrating bug in wxWidgets you will find that when you drag a class into or out of your group you will loose control of it. You'll have to grab it again to continue moving. I apologize for the inconvenience. As soon as there's a fix to wxWidgets I will update the KlassModeler.