With Shopify upgrading the Thank you and Order status page to Checkout Extensibility this year, additional scripts will be removed requiring us to move to Customer Events.
The issue is, according to this list, there is no event for a post-purchase orders.
Hello 
If the post-purchase triggers a new checkout, it should be tracked through the usual standard events.
DOM events can be used to track a user clicking on a button or link, but it’s true that not all elements will trigger these events on the checkout pages.
It would be easier to provide more guidance if you could provide more details into what you’re trying to track and where the customer events fall short, exactly.
Thanks 