The demo shown below was taken from the official Mermaid documentation.

mindmap
root((mindmap))
  Origins
    Long history
    ::icon(fa fa-book)
    Popularisation
      British popular psychology author Tony Buzan
  Research
    On effectivness<br/>and features
    On Automatic creation
      Uses
          Creative techniques
          Strategic planning
          Argument mapping
  Tools
    Pen and paper
    Mermaid

Textual representation

mindmap
root((mindmap))
  Origins
    Long history
    ::icon(fa fa-book)
    Popularisation
      British popular psychology author Tony Buzan
  Research
    On effectivness<br/>and features
    On Automatic creation
      Uses
          Creative techniques
          Strategic planning
          Argument mapping
  Tools
    Pen and paper
    Mermaid

The code above is rendered by "Prism Syntax Highlighter for Confluence" which supports highlighting Mermaid syntax.

👉 Check out the official Mermaid documentation here https://mermaid.js.org/syntax/mindmap.html.