It was decided that Member States should not be allowed to hide or delete sent documents in SFC2021. This is because once a document has been sent it is registered in many internal Commission workflow systems (and may trigger certain processes in these systems), and hiding or deleting in SFC2021 will not delete them in the other systems.
If the Member State sends the wrong document they should then send a correction document (if needed they will have to create a new version of the object and attach the new document).