SharePoint Framework Extensions Release Candidate 0 (RC0) is now available! In it, you will find several updates to Extensions based on your feedback and scenarios. For the Extensions APIs, you will see several changes to the Customizers and Command Sets that you can use to customize sites. Most particularly, we've changed the engagement model for Application Customizers to be event-driven to accomodate the variety of different page access patterns that we see happening. In addition, there are several improvements across the board to #SPFx, including updates to support TypeScript 2.4, improved property pane behavior, and beyond. Find out more in the release notes for #SPFx version 1.2, and view our updated documentation which include all of these changes.
We look forward to your feedback as we move towards General Availability, which you can provide in this TechCommunity or on Github. Happy coding!