You're right, managing different packaging units in purchase orders and inventory is a common scenario, and Odoo offers several ways to achieve your desired outcome without product variations. Here are the solutions:

1. Purchase Orders:

• Purchase Order Lines with "Packages":
  • Instead of setting up a product packaging, create a separate "product" in Odoo specifically for the "box of 10" unit. This product should have a base unit of measure (e.g., "Box").
  • On the purchase order line, select the "Box" product and enter the desired quantity (5 in your example). This will reflect as "5 boxes" on the order line.
  • Ensure the purchase price of the "Box" product reflects the cost of 10 units, so you don't need to manually adjust calculations.
• Purchase Order Lines with "Quantity UoM":
  • If your Odoo version supports it, use the "Quantity UoM" field on the purchase order line. Enter "Box" as the unit and 5 as the quantity. This will display "5 Boxes" on the order line.
  • Remember to set the "Conversion Factor" between your base unit and the "Box" unit (e.g., 1 Box = 10 Units). This ensures accurate inventory updates.

2. Inventory Conversion:

• Routing Rules:
  • You're correct, routing rules allow for unit conversions during stock moves. Create a rule that triggers when receiving the "Box" product.
  • Set the "Source UoM" to "Box" and the "Destination UoM" to your base unit (e.g., "Unit").
  • Define the "Quantity" conversion using the conversion factor (e.g., for 1 Box, move 10 Units to inventory).

• Consider using the "Product Packaging" feature only for internal tracking without affecting purchase orders and inventory.
• If managing multiple packaging variations for the same product is necessary, explore product variants or custom development options.
• Consult your Odoo documentation or system administrator for specific configuration details based on your version and modules.