How do I quickly see which products are out of stock?

There are two quick ways:

• Inventory → Out of Stock lists every SKU at or below your out-of-stock threshold. Use the Overall, Warehouse and Store tabs, search by product, SKU or barcode, and download the list with ⬇ CSV or ⬇ Excel.
• Products → Manage Products: open Filters and set Stock to Out of stock.

The Inventory list reads your warehouse and store stock. Set its threshold under Inventory → Inventory Settings. The same page has Show out-of-stock products on the storefront, if you'd rather hide sold-out items.

The Inventory menu depends on your plan. If you don't see it, use the product list filter.