Details
Description
In ACT-26 embedded subprocesses where implemented in the core engine. See e.g. this test case for this: https://svn.codehaus.org/activiti/activiti/trunk/modules/activiti-engine/src/test/resources/org/activiti/engine/test/bpmn/subprocess/SubProcessTest.testDoubleNestedSimpleSubProcess.bpmn20.xml.
The Designer should be able to handle this as well.
Also please ensure that multiple nestings are possible and that boundary events can be attached to embedded sub-processes.