Yes, Payster works with draft orders.
First of all, make sure in the app's settings that the option to Monitor and remind draft orders is enabled.
Then, once you send the order invoice to your customer, the draft order becomes visible in the Payster dashboard. From that point forward, the draft order follows the same flow as regular orders within the Payster system. If you filled in the customer's contact info, they will receive payment reminders as per regular order.
How do you send a draft order invoice to your customer from Shopify?
Add products and a customer to your draft order and then click on "Send invoice".