dhtmlx Gantt: How to update parents automatically of a custom date column

My Gannt is constructed in the following way:

In the first column with a date on the image above, if I change the value of a lightbox, it updates the parents to the value earliest date by itself.

How could I configure the highlighted column to have the same behavior?

If you change the start_date or end_date parameter of a child task, the changes may affect its parent task with the project task type. But Gantt doesn't check other parameters. You need to implement a custom solution by using Gantt API and Javascript. The easiest way for that would be to use the eachParent method in the onAfterTaskUpdate event:

https://docs.dhtmlx.com/gantt/api__gantt_eachparent.html

Here is an example of how it might be implemented:

http://snippet.dhtmlx.com/5/66c4901d1