Mermaid does indeed provide alternative layout engines. Please do try ELK before Line9. My experience is 1) hand-tuning the layout of Mermaid, having to try alternative engines or parameters, is not what I want. I just want a graph that I can use straight away. 2) ELK more often than not does give a clearer flowchart that I might be satisfied with for personal use but I still wasn't happy putting it in a presentation in front of others.