Unfortunately this is not acceptable solution. Each data source item has fields (properties of the object) "title" (from Kendo default schema) and "Title" (from user fields). Since java script is case sensitive those fields represent different properties. There can be many other user fields ("Description", "ReminderDate", "TaskCost", etc.) and they are not intersect default kendo fields like "title", "start", "end", etc. What if I do not want do display default task title. I provide custom columns array without "title" field and get the same incorrect behaviour with summary tasks. Link with the example.
Nothing is written in the documentation
that "title" field is required
field in the "columns" array.
Since Kendo Gantt requires at least one column to be displayed I guess that correct behaviour with displaying summary tasks should be the following: display triangle (which expands children tasks) in the first table column (even if the first field in the columns array is not "title"). Can be such behaviour achieved in the latest (2014.3.1411) version?