I just launched a new app to help merchants create upsell offers on post-checkout (thank you page) and in the order status page.
The app has been picked by Shopify Apps Team as New & Noteworthy (thanks!) and it will be 100% free for the first 100 early adaptors:
Looking forward to your feedback!
Do you have a demo store, or at minimum screenshots of the configuration or example upsell on an order page?
Here is the demo store for one post-purchase offer:
And for the offer setup in the backend checkout the screenshots here: