I am trying to delete a OneNote Notebook. I cannot seem to achieve it.

1. In the upper-left corner of the page, select the   App Launcher and select    OneDrive.
2. Navigate to the notebook you want to delete. It's probably under Home> Recent, or My Files > Notebooks. You can also type the name of the notebook in the search box at the top.

This finally worked but most recent files cannot be deleted from the list you have to search for it in this interface then delete it. Should not be so difficult??!!

There is never the option to delete these files. It does not give you that option even after closing the notebook. As with others there are no notebook files found in the default backup folders either. Where are these files and like others why is this not simple enough to do??!!

Go the My Content page. Click the 9 dots are the top right, click "See all my content" https://www.microsoft365.com/mycontent?auth=2&home=1&section=recentdocs
If it's in the recently opened, you can find it easily; otherwise, you can search the name.

Hover over notebook, click the ... and click Delete.

I think I found a solution.

1. In OneNote, navigate to your list of notebooks. Right click on the one you want to remove and 'close' it.
2. Browse into the 'More Notebooks' area, then right click on the notebook you want to delete and select 'Open File Location'

Here's the weird thing, it looks like notebooks are actually stored as hidden folders that can only be viewed while trying to open them through this interface.

3. Locate the 'folder' for the notebook you are trying to delete, select it and hit delete, a message box will pop asking if you want to permanently delete...
4. Cancel out of the Open Notebook window.
5. You will still need to remove the name of the notebook from any recent notebooks list but it should be gone.

Give it a go...

If using OneDrive, OneNote shortcuts cannot be permanently deleted using File Explorer. Instead, after closing the notebook in OneNote, delete the shortcut via OneDrive Online.