How to add task extension?

Gantt
#1

Is possible to add a task extension field in gantt chart? If it never finish in the allocated days,I need to extend the days.

#2

Hi,
task data objects can contain any custom properties. You can add the appropriate columns to the grid and inputs to the lightbox to operate them

docs.dhtmlx.com/gantt/desktop__s … lumns.html
docs.dhtmlx.com/gantt/desktop__d … _form.html
docs.dhtmlx.com/gantt/desktop__server_side.html
docs.dhtmlx.com/gantt/desktop__l … properties