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Mermaid Live editor
https://www.mermaidchart.com/play
https://mermaid-js.github.io/mermaid-live-editor/edit

Documentation
https://mermaid.js.org/syntax/flowchart.html
https://jojozhuang.github.io/tutorial/mermaid-cheat-sheet/

Integration in MkDocks
https://squidfunk.github.io/mkdocs-material/reference/diagrams/

Examples