If a task doesn’t have start_date and duration/end_date parameters, it takes missing parameters from other tasks. So, you won’t see “” in the end_date column in the grid, and you won’t be able to move or resize the task.
If you try to unschedule such a task, it will still have start_date, end_date and duration parameters, but by default, they won’t be displayed in the grid. So it won’t be possible to know which task didn’t have that parameter before the parse unless its name was different or unless you save it into another property of the task: http://snippet.dhtmlx.com/9b64a3663
The second question was answered in another topic:
Thanks for the solution, but this issue is not working. I want that if I don’t fill the end date and duration it should be seen as empty. End date should not be one day more than Start date. Also, it should not be as a mile stone.
It is not possible to have only “start_date” parameter. If there are start_date and duration or end_date and duration, Gantt will calculate the missing parameter next time you update the task.
It will only work if there is no both start_date and end_date: http://snippet.dhtmlx.com/412092d5d
If you still want that, you need to use different names for start_date and end_date, for example: starting_date and ending_date. Here is the snippet, demonstrating how it might work: http://snippet.dhtmlx.com/26e7b3ab5