The layout of the timeline might be refresched any time (more precisely - when something changes in the scheduler). If you append html manually - you’ll have to trace redrawing of the scheduler and reapply html every time. Html defined in the template function will be applied always
There is no built-in way to prevent expand/collapse of tree timeline items, so stopping event propagation is the only way.
Get a guaranteed answer from DHTMLX technical support team
under the most suitable support plan