Good to see you in the Community. I'm happy to help share some information about printing a joint check in QuickBooks.
Currently, the option to create and print joint check in QuickBooks Online is unavailable. We can only cater to one customer or vendor per transaction.
As a workaround, you may want to try recording them using a clearing account to debit the joint check account with the deposit and credit the joint check account with the payment. This way, your QuickBooks data file is correct because it has shown the payment from your customer and the payment to your vendor and the net result is zero in this account.
You may want to check one of my colleague's post for the steps: Creating a clearing account.
I also suggest consulting your accountant in other ways to record them. Your accountant can provide more advice about this to make sure your books are recorded correctly.
For future reference, you can also visit the QuickBooks Blog to see the latest product enhancements and get some tips on how to manage the business using QBO.
That should point you in the right direction. Stay in touch if you have additional questions about QuickBooks Online. I'll be happy to help you. Have a wonderful day.