jBPM Web Designer focuses on BPMN2 nodes that are supported by the jBPM runtime. Collaborations are currentrly not yet executable by the runtime and are not included in Designer. You could model such business process using the new Eclipse Modeller however it would not be an executable process.
You can still have multiple swimlanes in your process, thats no problem, however currently a single pool is supported by the runtime (which is the canvas/drawing area in Designer)
HTH