https://www.telerik.com/kendo-jquery-ui/documentation/api/javascript/ui/gantt/configuration/columnresizehandlewidth
columnResizeHandleWidth - API Reference - Kendo UI Gantt - Kendo UI for jQuery
In this article you can see how to configure the columnResizeHandleWidth property of the Kendo UI Gantt.
api referencekendo uiganttjquery