Reply To: RE: Attributes of attributes
The best way is to choose Entity Relationship Diagram (Project/Add Diagram/Other/Entity Relationship Diagram). Insert an entity to your diagram, add an attribute, right-click on it and choose Primary Key, Foreign Key, Nullable or Auto Increment from context menu.
If you want to use UML Class Diagram, you can add an attribute with custom stereotypes to a class. You can create custom stereotypes for foreign key and auto increment (right click on attribute / Field Properties / Stereotypes tab). You can use (UML) standard modifier 'ID' for primary key (right click on attribute / Field Properties / Modifiers group)