shows the chart (timeline) area of the Gantt chart
//hides the timeline area of the Gantt chart
gantt.config.show_chart = false;
gantt.config.show_chart = false is useful when you need to hide the timeline area of the Gantt chart quickly while gantt.config.show_grid = false serves to hide the grid area. If you work in a simple layout, you'd better not use these two options together as it may cause an unexpected result. Instead of it, you should change the configuration of the layout via gantt.config.layout.
The show_chart config will only work if you have not changed the default configuration of the layout via gantt.config.layout. In case you have configured a custom layout, then you have to create several custom configurations and to switch between them to hide/show the chart.
Related sample: Gantt. Toggle timeline (custom layout)