Assigning section level permissions in OneNote

So you have multiple people editing a OneNote notebook in SharePoint Online, but you want section level permissions (only certian people can edit their own tabs).

There is a way to break permission inheritance on each tab!

1. Navigate to the document library where the OneNote notebook is stored
2. Copy the URL into Notepad
1. Example: https://thenetworg.sharepoint.com/teams/int0005/SiteAssets/Forms/AllItems.aspx
3. Modify the URL to contain the Notebook's Name
1. Example: https://thenetworg.sharepoint.com/teams/int0005/SiteAssets/Forms/AllItems.aspx?id=%2Fteams%2Fint0005%2FSiteAssets%2FSite%20Notebook

Notice how the bold parts are the URL to the notebook, escaped by the character %2F

This will get you to the library where you can see a view with each section as its own item. 

Now you can break permission inheritance on each section and give unique permissions!

Source: https://blog.thenetw.org/2018/06/18/protip-assigning-section-level-permissions-in-onenote/