Hi Ori,
Yes, it's possible.
If both of your accounts have Office 365 subscription, it will be much easier.
Please follow the steps below:
1.Open the notebook you want to move in OneNote 2016.
2.Click File > Export > Notebook > OneNote Package and Export this notebook.
3.Sign out your account A, and sign in OneNote 2016 with your account B, go File > Share.
It will alert you that this notebook have to be saved on OneDrive or SharePoint before sharing.
4.Click OneDrive and browse a location where you want to save this notebook. After the syncing process is finished, then you have already moved this notebook.
Meanwhile, I would like to mention, in this way, the changes you have made on this notebook won't sync to account A's notebook. If you want the changes to be synced ,
you can just share this notebook to account B.
Regards,
Alex Chen