Hi,
I have more than 10 years experience in php, wordpress, gravity form.
From what I understand you want:
1) Transfer all existing entries from Gravity to ShipStation (use manual import) to 'Manual Import' category
2) Fix the trigger in Gravity Form that send data to Zapier, there is a bug in the trigger that send the wrong data.
Could you please explain the problem with entries already be sent to ShipStation?
Thanks