Your confusion ends here, @Imtired.
Allow me to fill you in on everything you need to know about matching bank transactions in QuickBooks Online (QBO).
When matching downloaded transactions in QBO, the system will show all the possible transactions you can match based on the amount. Thus, you'll need to search each of the open invoices and match them manually to your downloaded transaction.
On the other hand, there isn't an option to turn on or off not to show all the open transactions that match your downloaded one. However, you can utilize the Bank rule feature to automatically categorize your bank transactions. For more guidance, feel free to check out this article: Set up bank rules to categorize online banking transactions in QuickBooks Online.
Once all your transactions are matched, you can reconcile your account when you're ready. This is to make sure your QuickBooks transactions match your bank statements.
It's nice working with you, @Imtired. Should you need further assistance matching your bank transactions, I'm available here to help any time!