Yes, you have full control over your auction. To hide or delete an item, you have two options. You can click the 'eye' icon, which will hide the item and make it no longer visible to the public. Or you can click the trash can icon, which will delete the item.
If an item already has bids, deleting the item will stop it from being processed at the end. We would recommend doing this only in rare occasions (such as having a gift-card as an item and the business no longer exists), and always in communication with the bidder. Clearly, if the item has no bids, it can also be removed or hidden seamlessly without any effect on the auction or anyone that has participated.