Hello Shibhit,
Indeed the drag handler is not usable in this scenario, because the default rendering of the task in the timeline view is overwritten. This behavior is expected because of the overwritten html that is used to visualize the task. In such scenario you can only show the progress of the task (like in the demo), but edit it trough the popup editor of the task.
Hope this information helps.
Regards,
Nencho
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