flow Flow1
   call Flow2 with para2;

flow Flow2
   inSlot
      inputPara para2

flow Flow1
   call Flow2 with Flow2.para2

flow Flow2
   inSlot
      inputPara para2

Flow:
"flow" name = ID
   ("inSlot" inSlots = InSlot)*
   ("call:" calledFlow = [Flow|FQN] "with" callPara = [Parameter|FQN])*
;

InSlot:
   "inputPara" parameter = Parameter
;

Parameter:
   name = ID
;

public class MyQNP extends DefaultDeclarativeQualifiedNameProvider {
	
	QualifiedName qualifiedName(Parameter p) {
		return QualifiedName.create(p.getName());
	}

}

public class MyDslRuntimeModule extends org.xtext.example.mydsl1.AbstractMyDslRuntimeModule {

	@Override
	public Class<? extends IQualifiedNameProvider> bindIQualifiedNameProvider() {
		return MyQNP.class;
	}
	
}

flow Flow1
   call Flow2 with para2  

flow Flow2
   inSlot
      inputPara para2


flow Flow3
   inSlot
      inputPara para2  //with your solution this doesn't work