Hi GLF2,
QuickBooks Online is designed to help make running your business simple. I know how important it is to keep on top of things like partial payments or instalments your customers make towards their invoice. I'd be happy to shed some light on the options available to you in QBO.
Recurring Transactions are really helpful, and they can ensure your business bookkeeping is as organized and efficient as possible. While there's a number of transactions for you to select in the Recurring Transactions feature, you're unable to set up reminders for payments. This is because you're meant to wait until the customer's payment hits your bank account in real-life, before recording it in QBO. If it were to be recorded before then you may run into confusion or discrepancies in your books.
If you were issuing multiple invoices, you could set up a recurring invoice. However, since you're going to be applying multiple partial payments, the recurring transactions/reminders tool wouldn't fit your needs. I'd suggest setting up a reminder outside the QuickBooks environment so you don't forget to record a partial payment instalment or remind your customers to send said payment.
If this is something you'd like to become available in QBO, I'd suggest submitting your feedback to our product development team for review. You can do this by clicking the Gear icon > Feedback. We're always searching for new ways to improve the product.
Have a great day.