Collections on enter.market is not the same as on enter.art/enter.audio. Learn the difference here.
Collections on enter.art and .audio are modular and can be changed after the creator's visual liking. This means that you can add and remove NFTs you own in and out of any collection as you please.
Collections on enter.market are permanent and tied to the smart contract they were minted from. NFTs from a specific collection can always be traced back to the collection. This means that a collection can be moved from one marketplace to another, as long as the smart contract is supported.
Want to learn more about enter.market? Check out this article!