Hi @BABY_JOJO
Unfortunately, the search engine that OneNote desktop app is using does filter out special characters.
Here is a similar thread in Microsoft Feedback Community, "Search in OneNote Desktop should not ignore special characters", you may vote it up to help Microsoft engineers have a better visibility on what issues that you’re experiencing with Office product and which features are most important to you.
Thanks for your understanding.
Besides, if needed, you may try OneNote for Windows 10. Based on my test, the special characters can be searched as the image below.
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