Ted here from Shopify, thanks for posting your query!
So you should be able to close a development store as mentioned in this guide. Once closed, the store name will remain in your list of development stores (in your Partner account) and there currently isn't a way to remove an inactive account from this area. The status will also change from "Active" to "Plan changed" and you will no longer have access to the store's admin. Can I ask why you would like to close your store?