This is a demo tutorial. While there is no step-by-step commentary available (yet), the live demo below is fully functional. Feel free to open it for full source code.
Axis ranges are data items, so they can be added directly to a Legend data. This demo shows how we can also enhance that capability to replicate axis range appearance in legend markers with custom template setup function.
Demo
See the Pen Adding axis ranges to a legend by amCharts team (@amcharts) on CodePen.