That's called a variation listing, only available in certain categories. It is intended to list variations of one item, such as different sizes, or different colors. It is not intended for sellers to offer choices of several different items, and is actually a violation of eBay policy to do so. Obviously that is not viorously enforced, but potentially the listing could be taken down, and repeated takedowns could lead to suspension.
List more, sell more. Goodwill that other, uh, stuff.
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