In Katana, you can add products to the Product recipe / BOM of another product. This is called a subassembly.
A subassembly in Katana is no different from any other product, you can switch batch tracking ON for a product that is used as a subassembly.
Katana enables you to track batch information for ingredients used in manufacturing. When you complete a Manufacturing order for a product that includes a batch-trackable product as an ingredient (subassembly), you need to select the subassembly from a specific existing batch. This works in the same way as selecting any other ingredients (e.g. materials) from batches when completing Manufacturing orders.