I've got some other steps in deleting a duplicate journal entry, @kimfurry.
In addition to LorriTES suggested, you’ll want to click the Magnifying glass icon to locate and delete duplicate Journal Entry (JE). Let me guide you how to do it in your QuickBooks Online (QBO) account.
Click the Magnifying glass icon.
Enter the date, amount, or transaction number you’re looking for then select the desired transaction
Select Advanced Search if the transaction you’re looking for does not appear in the result.
Adjust the filters to find the duplicate journal entry.
Once done, select the duplicate JE.
Click More and select Delete.
You can also check this article that provides the complete details in using the Advanced feature in QBO: Search for transactions.
I also recommend consulting with your accountant to ensure the accuracy of your accounts after deleting the duplicate.