In OneNote Online, you can add a new section to better organize by grouping related pages.
At the bottom of the page list, click + Section.
In the Section Name dialog box, type a meaningful description for the new section, and then click OK.
You can organize sections by dragging their names up or down in the list.
Note: Keep in mind that you can't currently create subsections or section groups in OneNote Online.
Tip: If you accidentally create a section that you don’t need, right-click (PC) or Control-click (Mac) its name, and then click Delete Section.