A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
With around 50 notebooks, I’d recommend keeping a dedicated notebook index for quick research access. This takes some initial setup, but gives you a list you can organize yourself rather than relying on recently opened notebooks.
Here are some suggestions you can try:
In the desktop OneNote app, select File > Open and check Open from other locations if any notebooks were saved outside your usual location. This provides another route to notebooks stored elsewhere, although it is not a guaranteed complete inventory.
Create a page called Notebook Index in a notebook you use regularly. Right-click each notebook’s name, choose Copy Link to Notebook, and paste it onto that page. OneNote pastes the notebook’s title with a clickable link. Repeat for each notebook as you locate it.
I’d arrange those links alphabetically or by research topic, with a short description beside each. Keep adding newly located notebooks until all 50 are accounted for. The index won’t discover missing notebooks automatically, but it gives you a practical starting point for future research.