I want to model activities on different levels of granularity. Each level has its own activity diagrams. The top level diagram describes a process most abstract. I want to describe a sub activity more detailed with another activity diagram. I want to navigate through these diagrams. This is actually the concept of sub diagrams. But in my version (4.0, modeler edition) there is no possibility to add sub diagrams to activity diagrams in UML 2.0 projects.
What do I do wrong?
P.S. It works with UML 1.x projects.