UX improvement - hiding the side panel

Syed Habib and many others requested the two UI changes bellow

1. Please move the left pane away, which is serving as a menu now, it’s taking valuable space for just setting up the menu, which you can usually set at the top bar.
2. Please make 3 left panes (as it is in OneNote, so you can expand the category (next layers of folders) in the next pane and one body for the notes. These panes should be expandable/shrinkable/custom sizeable.