Perhaps I need to rephrase the question.
You are asking to roll up a summary of the child Tasks up to the Parent project record. I have made the assumption that there are multiple Tasks as child records to each Project.
You are saying that you want to show the start date of the respective tasks and the field that holds the date is called [Design Start Date].
Is there is a field you want to use which has an identification of what the task is?
I�m assuming that you would have a field called something like Task Name or Description.
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