Question
Can the eBay store search be customized so it only searches a catagory?
Answer
By Category, I am assuming you are referring to your custom category.
1) Go to the eBay Stores home page
2) Click on the "Search" button
3) Click on one of your custom categories
4) View the source HTML and search for the following phrase:
http://search.stores.ebay.com/search/search.dll
Copy the HTML from the first table tag you see previous to this phrase, until the first table end tag you see after this phrase.
By default this will check titles and descriptions, but if you do not want to check that, you can just deselect the checkbox and click on the "Search" button before you view the source HTML.
Personally, I prefer "Shop by Category" links since buyers will be able to see all your other custom categories.
I hope this helps.