How do I "pay a bill" with a "note payable" account? I had to create an "unknown bank" account until I found out where the money was coming from. Thanks!

Welcome to the Community, @DeniseRBBD.

I’m here to share some information on how to pay a bill in QuickBooks Online.

Since you don’t know where to post the transaction, we can use the unknown bank (holding bank) to pay for the bill in the meantime. By using Pay Bills, an entry is created that will affect Accounts Payable and the specified bank account.

Here’s how:

1.    Click the Plus (+) icon at the top and select Pay Bills.
2.    Select “Unknown  Bank” as your Payment account.
3.    Select the bill.
4.    Hit Save.

For more information, you may take a look at this article: https://quickbooks.intuit.com/community/Income-and-expenses/How-to-enter-and-pay-bills/m-p/186102.

Once you've verified the bank used to pay for the transaction, you can make a deposit to transfer the funds back to Unknown Bank. To do that, follow the steps below:
1.    Go to the Plus (+) icon and select Transfer.
2.    Click the Transfer Funds From drop-down to select the bank where the funds are taken out to pay for the bill.
3.    On the Transfer Funds To, select Unknown Bank.
4.    Enter Transfer Amount.
5.    Click Save and close.

That should be it. Feel free to leave a comment below if you need anything else. I’ll be here to help. Wishing you the best!