In Mirakl, you have the possibility to "refund", i.e. to cancel an order after it has been accepted.
In the My Orders menu, click on All Orders.
By clicking on an order number, you will have access to the details of the order.
In the top right-hand corner, by clicking on the refund button, a window with the details of the order will appear.
You can cancel the entire order completely or cancel partially each product in terms of quantity.