OneNote has an inherent issue when it comes to keeping organized...notebooks. It's not that I'm saying notebooks are a bad way to keep things together. Quite the contrary. The problem comes in with what do you with the crabgrass-like growth of the number of notebooks you have as your time with OneNote grows. Here are the five steps I recommend when you're ready to get rid of a notebook. (Please note these steps require OneNote 2016 to execute completely.)
Step 1 - Transfer old content
Before you delete an old notebook make sure you've gone through and transferred any content you need to retain to a new notebook. You could go through and move things item by item but to save time I recommend creating a section for all the pages you plan to move in the notebook, moving the pages to that section, copying the section to the new notebook, then deleting the section. That extra copy may seem counter-intuitive, but it gives you an extra bit of security in the move in case something goes wrong.
Step 2 - Export to PDF
You can export an entire notebook to a PDF file for easy storage. I recommend this over creating a OneNote package since at this time you've already decided to delete the notebook so you won't need to have the content in an editable format. Exporting it as a PDF file gives you the reassurance of having access to the information in the smallest and most portable format possible.
Step 3 - Create an Archive Notebook
Sometimes we need to keep the content in OneNote format but we don't need the content in separate notebooks. In these cases I'll use an Archive notebook. I create a section in the Archive Notebook for the content I am archiving from the old notebook and then move that content over. Once I'm done I have an organized Archive notebook, access to the content I need, and one less extraneous notebook file to keep track of.
Step 4 - Create a link index
One of the tricks with OneNote is you can create links to notebooks, sections, pages, and even content on a page. By creating a master index notebook you can create links to all the content you may need access in a rarely used notebook, clicking on the links to access the information, while reducing your sync load and storage needs. I recommend this highly for content you may need access to while on mobile but can live without if you're offline.
Step 5 - Leave it alone
If you're using a system such as OneDrive to store your OneNote files, it might be best to not delete notebooks unless you absolutely need to. You can move them to other out-of-the-way folders, but by keeping the files you can leverage the OneDrive search capability without having to open the notebooks every time.
What you need is a plan
Notebooks are one of those things in OneNote that can be extremely powerful...with some planning. Without a plan as to how best to put them to use, be prepared to become your own librarian.
What do you think? Talk about it over in the TIP Community.