Microsoft just released the latest Windows 10 Insider build for the Fast Ring, build 14267, along with a helpful list of new features that come along with it. While there's nothing as significant as the long awaited appearance of Edge extensions, the new build does provide some useful new stuff, including:
Easier music search in Cortana: Click on the new Music icon in Cortana, at the top right corner, while you're listening to a song, and Microsoft's personal assistant will try to identify the song for you
Edge Favorites Bar improvements: Edge's newfangled Favorites UX, the Favorites Bar, gets folders, and an icons only view.
Clear Edge browsing history after each session: In Edge Settings, you can now set "Always clear this after I close the browser” in browser data settings.
Download prompts are improved in Edge: You can now choose where to save a file when downloading via Edge.
Messaging + Skype improvements: Attach photos, or take a new one, with a single click in a Skype conversation
If you're in the Fast Ring as a Windows 10 Insider, you can check Settings>Update, and get to downloading the latest build now.