Welcome to the Community, @EjazU. I'll share some details about the pre-fill option in QuickBooks Online (QBO).

Once the Pre-fill forms with previously entered content to enable auto-recall option is enabled, you'll receive a prompt (Do you want to prefill this expense and overwrite your entries using values from this contact’s last expense?) whenever entering a new expense for that specific vendor name. 

If you click Yes, the program will prefill the details of the form based on the information on the recent expense transaction previously created for that vendor name. 

If you input new details for that expense transaction and receive a prompt when selecting the vendor, you can choose No so QBO won't overwrite the details. 

For reference, check out this article: How to use auto-recall to pre-fill transactions.

I also added this helpful article in case you need to create recurring expense for a specific payee: Create recurring transactions in QuickBooks Online.

Should you have other questions or anything you want to know about creating expense in QBO, please don't hesitate to leave a reply below. The Community is always open to ensure your goals are achieved.