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

sankey-beta

Electricity grid,Industry,342.165
Electricity grid,Lighting & appliances - commercial,90.008
Electricity grid,Lighting & appliances - homes,93.494
Gas,Thermal generation,151.891
Liquid,Industry,121.066
Liquid,International shipping,128.69
Liquid,Road transport,135.835
Ngas,Gas,122.952
Nuclear,Thermal generation,839.978
Oil imports,Oil,504.287
Oil,Liquid,611.99

Textual representation

sankey-beta

Electricity grid,Industry,342.165
Electricity grid,Lighting & appliances - commercial,90.008
Electricity grid,Lighting & appliances - homes,93.494
Gas,Thermal generation,151.891
Liquid,Industry,121.066
Liquid,International shipping,128.69
Liquid,Road transport,135.835
Ngas,Gas,122.952
Nuclear,Thermal generation,839.978
Oil imports,Oil,504.287
Oil,Liquid,611.99

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/sankey.html.