Did you feel tired with your Scrum Board which has over 20 columns and the flow is complex? If yes! It's right time for you to look back and remove the complexity, the reason we do Scrum is dealing with complexity, not make it bigger!
From my old post about "Definition of Workflow", some people asked me to write more details about "how to apply it", how to have a Workflow to maximize the value of a team. I asked back to them, and answers always lead to the topic: Don't build team workflow by yourself just because you are a manager. It should come from the need of your team.