Welcome back to the QuickBooks Community, BethFL. I'll be sharing further details on how Workflows works in QuickBooks Online. Let me also ensure you can achieve your goal by performing the alternative steps below.

Utilizing workflows in QBO helps you automate common tasks in QuickBooks like sending payment reminders to customers. Also, the details below are some common uses for workflows for customers:

• Automatically send unsent invoices: Send your customers invoices that haven't been sent yet.
• Payment received: Automatically email customers to let them know you received their payment.
• Payment due reminder: Automatically email customers to let them know their invoice payment is due soon.
• Overdue invoice memo: Automatically update an invoice message with an overdue or customized stamp.

With the information mentioned above, setting up the Workflow to only send statements to customers with an open balance is currently unavailable.

However, you can create and send customer statements manually in QuickBooks. This shows the outstanding balances or invoices that will soon be overdue.

Here's how:

1. Go to the Customers and leads menu on the left panel.
2. Choose Customers.
3. Select the customer you want to make statements for. 
4. Choose the New Transaction dropdown and select Statement.
5. Review the customer’s email address, then click Save and close.

Then, you can open this article if you need steps on how to make multiple statements for your customers: Create and send customer statements in QuickBooks Online.

Lastly, refer to this article on how to view the status of all sales transactions such as open and paid invoices in QBO: View sales transactions in QuickBooks Online.

Please comment down below if you have further concerns about sending customer statements in QuickBooks Online. We're available 24/7. Stay safe, BethFL.