Property sets feature in the Google Search Console enhancements expands to cover more reports. Property sets, which was launched in May this year, show how a business is seen by Google across separate websites or apps.
Additionally, you can also monitor your site's hreflang setup across different versions of the same website during a planned transition, such as when you move from HTTP to HTTPS, or change domains.
For example, if you have multiple international or brand-specific websites, and perhaps even an Android app, it can be useful to see changes of the whole set over time: are things headed in the expected direction? are there any outliers that you'd want to drill down into?
With this update, using property sets, you can now "add any verified properties to a set," as well as see "mobile usability report, review your AMP implementation, double-check rich cards, or hreflang / internationalization markup, and more," writes Google.
Here is a listing of some of the reports you can see: