I would love it if we would be able to change the order of our items in our chest, either by ourself (drag & drop) or by pressing a button ("show books", "show food", "show pets", etc. // "sort by price", "sort by store", etc.). That would make it much easier to see what you already bought (maybe combine this with a little note in the shops, that show you how many of that item you already own.)
This could also be an VIP feature, just like changing the order of your friendlist.
Customer support service by UserEcho