By clicking on the ‘YITH’ icon on the upper right side of the page, another button will show.
This way you will be able to preview the ‘Thank you’ page you are working on. Click on ‘Preview as YITH Custom Thank You Page’ to see a preview.
If you haven’t got any orders yet, the plugin will ask you to create a dummy order, so the Thank You page will show based on a ‘dummy order’. If you do have previous orders, the preview will show using a random completed order.