I've been using OneNote 2016 extensively, but I tried today to see how the modern, cross-platform OneNote would work. When I click Notebooks > More Notebooks from the Home tab, it shows several of my notebooks, regardless of their location. But every SharePoint Online site has a notebook, and my firm uses them, sometimes extensively. There is no File > Open option from the new OneNote, and clicking for more notebooks does nothing. I'm already logged in to my Microsoft work account, so there's no service to add. Searching for the name of a notebook--which Microsoft names as "[SiteName] Notebook"--does nothing. Is there no way to use the new OneNote to open an online notebook that has not recently been opened?