No, but you can place a second order.
Hold your order until you think it is complete.
We understand if stragglers join your group later, but if you need to order more, you will need to place a second order.
Note to group coordinators: I personally order extra of popular items when I coordinate a group, because I always have people come to me after ordering closes. It’s up to you whether you want to risk having excess items. If you find yourself in that predicament, you can offer the leftover items to your group. As my group has grown, I’m able to take that risk because someone will always buy the extras.