In Odoo version 16 , creating a backorder without validating the transfer is not supported by default. When you create a backorder for a delivery or a transfer, it is usually done to account for the items that couldn't be delivered or transferred due to stock unavailability.

However, if you still want to create a backorder without validating the transfer, you would need to customize the behavior and implement a custom solution. This may involve developing a custom module or making changes to the existing code.

Here are a few steps you can consider to achieve this customization:

1. Create a custom module or navigate to an existing module where you want to make the changes.
2. Identify the relevant models and views involved in the backorder process. This may include models such as stock.picking, stock.move, and views related to the picking process.
3. Override the necessary methods and views to modify the behavior. This might include customizing the create backorder functionality to skip validation or adding a new option to create a backorder without validation.
4. Implement the custom logic to create the backorder without validating the transfer. This could involve copying the relevant data from the original picking and setting the necessary flags or statuses to indicate that the backorder doesn't require validation.
5. Update the module, upgrade the database, and restart the Odoo server to apply the changes.

Please note that customizing Odoo's behavior requires development skills and understanding of the Odoo framework. It's recommended to carefully plan and test any customizations to ensure they align with your business requirements and don't introduce any unintended consequences.