When collaborating with a few different people within a parent card, often a few child cards may become completed or no longer relevant. Junking may not be appropriate in this situation as you may want to still find / reference this card later on. This is where archiving comes in. Archiving affects all users the card is shared with, and hides the card within the specific parent card it's archived in. It's easy to archive a card:
Once you archive a card, it won't immediately disappear. As soon as you refresh / switch views it will be hidden. If you want to see Archived cards again, just disable the filter which is active by default.
Note: An archived card will still appear in the Home / Collection views, archiving ONLY affects whether the card is shown when you are viewing within the opened parent view. If you would like to hide a card personally throughout Supernotes, mark it as 'Invisible'.