Swimlanes

[chrisbrayne]

Mermaid Feature Request: Native Support for Swimlane Diagrams

Is your feature request related to a problem? Please describe.

I'm always frustrated when trying to create true swimlane diagrams in Mermaid, as there is no built-in support for defining lanes that extend vertically or horizontally across the entire process flow.

Currently, users have to simulate swimlanes using subgraph, but this approach:

• Does not enforce strict vertical alignment of lanes.
• Does not provide clear role separation like traditional BPMN-style swimlanes.
• Lacks a structured grid format, making it difficult to track process ownership across departments.
• Requires excessive manual layout adjustments, leading to inconsistent and cluttered diagrams.

Given that swimlane diagrams are widely used in business process modeling, their absence is a significant limitation for users who need structured workflow visualization.

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Describe the solution you'd like

I would like native support for swimlane diagrams with the following features:
✅ Vertically or horizontally aligned swimlanes that extend through the entire diagram.
✅ Automatic role separation, where each swimlane contains only its assigned steps.
✅ A structured grid format that ensures clean alignment of process steps.
✅ A top-level title option for labeling the overall process (e.g., "Approvals Process").
✅ Smooth transitions across swimlanes, ensuring process flow moves left to right or top to bottom" while maintaining clarity.
✅ Customizable swimlane styling, including colors, borders, and column widths.

This would significantly improve Mermaid’s usability for business process modeling, approvals workflows, and organizational processes.

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Describe alternatives you've considered

I have attempted to create swimlanes using subgraphs, but this approach is:

• Cumbersome and difficult to maintain for complex workflows.
• Prone to misalignment, requiring trial and error to position elements correctly.
• Lacks automatic layout enforcement, forcing users to manually structure the diagram.
• Does not visually match industry-standard swimlane diagrams seen in BPMN or UML tools.

Existing alternatives outside of Mermaid include BPMN tools (e.g., Camunda, Lucidchart, Visio), but Mermaid’s text-based approach is much more efficient for dynamic documentation and version control.

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Additional context

Here’s an example of a manually created swimlane diagram in Mermaid:

While this mimics a swimlane structure, it is not natively supported and requires excessive customization.

By adding true swimlane support, Mermaid would become a powerful tool for business process visualization, making it easier to create professional, structured workflow diagrams.