You can use " insert related items " on one of the key classes and maximize the number of levels.
As an alternative, consider the following solution :
If (...) your classes are distributed between different packages and namespaces, so that EA generates several diagrams for them, you will have to combine them manually. Do this by opening both diagrams, selecting all (Ctrl-A) in one, copying (Ctrl-C) and pasting (Ctrl-V) in the other, then again ask EA about the layout scheme.
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