Glad to have you here in the Community, @WB19.

The ability to change the COGS Account Number without changing the account number for parts you sell for retroactive transactions is not available in QuickBooks Desktop.

If you change the COGS account number for parts you sell the account number change will apply retroactively and affect historical transactions using that account. QuickBooks Desktop applies changes globally across all instances of the account, including past, present, and future transactions. This is a consideration to keep in mind if you need to adjust reporting or keep track of historical data.
 

However, you have the option to add a note per parts item and enter a text or description you want to put. Here's how:

1. At the menu tab, click Inventory.
2. Choose Item list and double click the item you want to add note with.
3. Click New Note then enter description or text you want to add.
4. Then select OK to save.

I've also included this link in case you need them for your future business work:

• Track the products you manufacture
• Understand inventory assets and cost of goods sold tracking

Please let me know if you have other concerns or inquiries about managing your COGS account in QuickBooks Desktop. I'll be there to lend a hand. Keep safe!