Thank you for reaching out! As an Independent Advisor and fellow Microsoft user, I'm happy to assist you.
The reason you can't switch between noise canceling and ambient aware modes on your JBL BT700NC headphones when using them with Windows 10 is likely due to the lack of dedicated software or drivers for Windows. The JBL Headphones App, which allows you to customize these settings, is currently only available for mobile platforms like iOS and Android.
Without the JBL Headphones App on Windows, you're limited to the default audio mode, which in your case is "ambient aware." To change the mode, you would need to either use the headphones with a mobile device that has the app installed or wait for JBL to release a compatible version for Windows.
Please feel free to reach out if you require any additional assistance. I'm here to help!