To manually sort items, ensure your Filter is set to All Gifts. Then hover over Settings and select Visitor Setup. Under GIFT SORTING, select the Pencil icon next to Sort By: and click the drop-down to select Manual. 

Then return to your My Gifts page and hover over the item you would like to move. On the top right-hand corner, you will notice green arrows or a 4 arrow icon that you can click to drag and drop the item in its new location.