Not too long ago we introduced a toggle that allows you to preview the page and how it looks like before hitting the "Publish" button. Now you will be shown how the page will look like in a feed:
The preview will show you everything that readers will see when they meet your content for the first time.
Sometimes, you might not be happy how the default miniature looks like, e.g. when the interesting part of an image is not in the middle, or you want to focus on a different detail. In comes "Customize thumbnail":
This allows you also to have a News e.g. with only a Video and no image and still present an image in the feed, or to have a completely different image instead. You can then save, and preview your changes in the "Feed preview" area.