By design the height of a RadGanttView row is equal to the height of the grid area row.
Attached you can find a sample project demonstrating the deletion of a GanttTask child element. The project contains a RadGanttView and a button. In the button_click event handler we perform deletion of the first child of the first GanttTask.
Hopefully this will help you achieve the desired effect.
If however this solution is not suitable for you, I would need some additional information in order to understand the situation in more detail. What modifications did you make to include the rectangle described? How do you perform item deletion and how do you handle the rectangle resize?
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