We do not currently support accessing fields within insight objects. Only the following are supported as the moment as per this documentation.
You can access an insight field's full name, key, or summary through the following smart values:
issue.InsightField // returns Some Client Name (ABC-123)
issue.InsightField.key // returns ABC-123
issue.InsightField.summary // returns Some Client Name
Allow accessing all object attributes via smart values like
issue.InsightField.User // returns the value in the User attribute of the object