Gantt APITemplatesgrid_openOn this pagegrid_open Description Specifies the icon of the open/close sign in the tree column grid_open: (task: Task) => string;Parameters task - (required) Task - the task object Returns text - (string) - html text which will be rendered in the gantt Examplegantt.templates.grid_open = function(item) { return "<div className='gantt_tree_icon gantt_" + (item.$open ? "close" : "open") + "'></div>";};Related Guides Configuring the Tree Column Templates of the Grid