Select Database > Edit Current DBMS to open the DBMS Properties window, and then expand the Profile category in the left-hand pane.
If there is not an entry for Extended Object in this category, then create one by right-clicking Profile and selecting Add Metaclasses from the contextual menu. In the Selection box, click the PdCommon sub-tab, select Extended Object and click OK to add it to the list of objects.
Right-click the Extended Object entry, and select New > Stereotype from the contextual menu to create a new stereotype, which will be used to define your new object.
Enter the name of your new object and select the Use as metaclass checkbox. This will ensure that the new object appears in the PowerDesigner menus and has its own special browser category.
You can add attributes to the object, create templates to define its form for generation and reverse engineering, and produce custom forms for use in property sheets. For more information, see Extension Files.
Once you have defined your object, you need to enable its generation.