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.
By default when node with children is clicked it is "exploded" - children are shown. This demo shows how we can catch such events to automatically collapse all other open nodes when that happens.
See the Pen amCharts 4: Auto-collapse other nodes when node is exploded by amCharts team (@amcharts) on CodePen.24419