So I have some problems with this:
My first problem is that the window is really small for no apparent reason. You can only see 4 to 5 items at one time.
My second problem is that there's no way to search or sort or otherwise filter the list.
So here are my suggestions:
-Make the window taller. I'm thinking it would be sufficient if at least 10 items were visible at a time.
-Add a search function that lets you type in whatever you're looking for and only displays the items that match your search.
-Separate the item properties (price, quantity, seller, etc.) into columns, rather than with commas.