Ah, sorry for that. Yes, there are some elements that cannot be modeled right now, basically because they are not in widespread use or of unclear semantics. We have no plans yet to allow modeling these.
They can be imported (and dealt with) when created from another modeling tool, though.
As nikku emphasized beforehand, we currently don’t offer 100% bpmn coverage because of various reasons. If it would be just adding an icon to the Context Pad, we probably already had been implementing them.