Please follow the below steps to delete the CSKU from Catalogue Module-
Login to Selluseller >> Cataloge >> Click on channel SKU >> Scroll down find product listing management >> Search the marketplace and on right side you will find the arrow click on this and you will find the delete option for the SKU. Please refer the below attached screen shots for the same.
When the user deletes the product from Anchanto OMS UI, it will also be removed from the marketplace. To list it again, user need to restore it from the catalogue module > product listing page.