Unmap sales channels to hide unused catalogue items from designers

Unmap an item's sales channel to stop designers from seeing unused or unwanted catalogue items, and restore the mapping later if the item is needed again.

1. To stop designers from seeing unused or unwanted catalogue items, unmap the item's sales channel.

2. Unmapping the item's sales channel works for furniture items and other catalogue entries.

3. The mapping can be restored later if the item is needed again, so hiding is reversible.