Hi Tihomir,
Thanks for your information.
I fully understand that jBPM Web Designer just focus on an executable BPMN2 process model at level 3. And I also think such collaboration diagram is not needed at level 3.
Level 3 diagram only shows activties that the process engine cares.
However, collaboration diagram is used in Level 2 process modelling which is mainly for showing operational details and coordination details. I think Collaboration diagram is very useful for documentation and communication purpose. It's more for business users.
I can use Eclipse modeller for the time being, but I found jBPM Web Designer is just much easier to use compared to Eclipse one and have very good integration with Guvnor.