For Mac, how to automatically move Notes checklist items to bottom

Hi, CamPlom!

Thanks for visiting the Apple Support Communities. I understand that you're trying to have items in Notes on your Mac move to the bottom of a check list when you check them off, but don't see the option. I'm happy to help!

In macOS Catalina version 10.15.3, I'm able to view the option to sort checked items when I view the same Notes Preferences page your screenshot shares. Since I have confirmed it should be an option in macOS Catalina, I'd like you to follow the steps below to troubleshoot. Take the steps in order, testing between each:

1. Verify your current macOS version by selecting the Apple  menu > About This Mac. If you are not running macOS Catalina, or are running a version of Catalina earlier than 10.15.3, please update your computer, if possible (not all Mac models support macOS Catalina. If yours does not, update to the latest macOS version you can): How to update the software on your Mac - Apple Support.
2. If you're still not able to see the option to automatically sort checked items, the next step I can suggest is for you to quit any open apps: Quit apps on Mac - Apple Support and restart the Mac into safe mode: How to use safe mode on your Mac. See if you're able to set the option here.
3. Should safe mode not allow you to edit the setting, try doing so in a new, test user account: How to test an issue in another user account on your Mac - Apple Support.

Don't hesitate to respond back if you still need some help.

Best!

Thank you for follow up with us, CamPlom,

If you're having trouble updating from System Preferences, I can recommend locating macOS Catalina in the Mac App Store: ‎macOS Catalina on the Mac App Store.

Should you still have trouble updating, see if you're able to do so in safe mode: How to use safe mode on your Mac.

For more information on updating to macOS Catalina, check out How to upgrade to macOS Catalina - Apple Support.

Have a great weekend!