Settings › Inventory & Uploads › Locations holds your list of places, with sub-locations inside them (a case inside a room, a room inside a shop). Pick one on the item form, and filter Manage Inventory by it; filtering on a location includes everything in its sub-locations.

A location can also carry a standing website discount, and you can show each item’s location on your website and marketplace order pages, so whoever packs the order knows where to find it.