How does it work?
After registering you will receive an email with a link. Just click on that link and you will be logged in to your very own sandboxed test-admin-area. Open up a product, post or page and have a look at the preview functionality. Test everything to your hearts content and after 60 minutes the sandbox will be deleted again.
When editing products, just click “Preview Changes” to open a preview window.
In Gutenberg editor click on preview and then on “Preview in new tab”.