How to modify an order?
Click on the event, on the right sidebar click on "Order details". There, you will have a "Modify order" button at the top right corner. Modify as needed and submit for approval.
Keep in mind -
Try not to modify orders in the last minute, your supplier won't like it
In order for the change to take place you will need to wait for the supplier's approval
Once you have made a change, the order's color will switch to pending changing approval (orange color)