Chaining fanouts in workflow

[Tornhoof]

How can I add edges behind a fanout workflow step?, e.g. either add another executor which then processes further, or even preferred add additional fanout edges behind it?.

 var workflow = new WorkflowBuilder(orchestrator)
     .AddFanOutEdge(orchestrator, [.. researchAgents])
     .AddFanInBarrierEdge([.. researchAgents], collector)
     .AddFanOutEdge(collector, [.. summaryAgents])
     .AddFanInBarrierEdge([.. summaryAgents], synthesize)
     .WithOutputFrom(synthesize).Build();

In the example above, the researchAgents are collected in the collector and then again fan-out for the summaryAgents. This is adapted from the map-reduce example.
But what I'd actually like would be to have another fan-out and fan-in for each researchAgent targeting their own share of summaryAgents without going through the fan-in step.