Google started showing toolbar for Google Docs, for a quick access of shortcuts and formatting options. By using @ you can select all the quick tools in your document. Before, you could use @ to collaborate, but now it shows more options for creating content options on the document as well as formatting options. This unlocks more power tools for users using google docs. As new features will provide easier and faster access to find the right tool you look for right in the document. This evolves the distraction-free writing of google docs. As now, you can make your document fullscreen and use the quick access @ for any option you require.