The Edit & Preview menu needs to be established in 1.0
The full version will later connect to a tabbed inspector to provide customization options of both the preview and edit modes.
To the right of Menu and Navigate, a third top-level menu must be included: "Edit & Preview"
The 2 parts (50% width each from far left to Inspector border) are labelled "Edit content" and "Preview central"
For the 1.0 release, the available items in the menu are:
Background of the tab and menu area below: #141414