How to edit COGS post sale

Hello there, @Need2Learn. 

Thanks for sharing your concerns with us today. We can create a journal entry to edit COGS post sale. 

Here's how: 

1. Go to the Company menu, then select Make General Journal Entries.
2. Enter details in the fields to create your journal entry. Make sure your debits equal your credits when you’re done.
3. Click Save or Save & Close.

For proper posting of transactions, I'd recommend consulting with your accountant. 

Additionally, here's an article with more information in tracking your cost of goods sold in QuickBooks Desktop (QBDT): Understand inventory assets and cost of goods sold tracking.

Get back to me if you have additional concerns. I'm always around to help you more.

Would this solution show the correct COGS in the Reports, or it would just balance out the accounts that the preorders were tied to? I'm not sure how to properly create a journal entry for this

At this point, you can't get the Sales By Item Summary report to show the correct COGS since you sold them after receiving them at $0 cost.

A journal entry may not be needed depending on how you recorded the bill for the items.  What account did you assign the vendor's bill to: inventory, COGS, or something else?  

If you received it as COGS or another expense account, there's nothing else you need to do except to realize there's a possible mismatch of timing between when you booked the expense for the items received and the sale to the customer.  Maybe no big deal depending on your business.

If you received the items as inventory, then you need to make a journal entry to get the items out of inventory and book the COGS expense.  You would debit COGS and credit inventory for the cost of the items.  If you create a journal entry, it will correct your P&L (most important), but your sales reports for that particular sale will still show a $0 item cost.