When you copy a Change Category, the content in the "3. Auto Assignment" tab is not copied as follows:
The screenshots below are an example of an original Change Category named Add.IT.Workstation with information set in the "1. Properties", "2. Workflow" and "3. Auto Assignment" tabs.
The screenshots below are the copied Change Category named Add.IT.Workstation1 with each tab. The contents of the "1. Properties" and "2. Workflow" tabs matches the original Change Category. But the "3. Auto Assignment" tab is empty.
This behaviour is by design. The "3. Auto Assignment" tab's content is not copied. You will need to set the appropriate settings in this tab for the new category.
Also, when you select "Copy" by right clicking on the original Change Category in the Change Category list, you will see the following. At this time, the "1. Properties" and "2. Workflow" tabs are empty. The content of both tabs will be copied when you click the save button. This behaviour is also by design.