You can sign in to 2 accounts in OneNote. Open the corresponding notebooks in your accounts separately. Then copy the notebook in Account 1. Paste the notebook structure into the corresponding notebook for Account 2.
See: How to Transfer a OneNote Notebook from One OneDrive Account to another OneDrive Account? https://www.onenotegem.com/a/documents/gem-for-OneNote/Right_Click_Menu/2022/0405/tansfer-notebook-from-one-account-to-ano.html