Hello Shobhit,

I am afraid that we are not aware of such an issue, do you replicate the problem with our online demos below?

https://demos.telerik.com/kendo-ui/gantt/task-template

If not, please specify how your implementation differs from the demonstrated one.

Regards,
Nencho
Telerik by Progress

Hi Nencho,

thank you for the reply,

In the demo link you shared, you can see yourself that there is no option to adjust the percentage completed now.

however in the basic demo we can adjust the percentage completed.

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
Telerik by Progress

Dear Nencho,

Thank you for the information,

One more question. How to add custom validation to the datasource start date field in kendo gantt with a custom message to show?

Hello Shobhit,

You can declare the validation rules as part of the data Source schema.model configuration as explained in the following documentation article: DataSource Schema.model configuration

Other resources you might find helpful are: 

• kendo.data.Model Api reference;
• Validator - Overview;

Regards, Peter Milchev
Telerik by Progress