If you still use Secure Notes in Keychain Access, you can still use it, but not recommended

https://lapcatsoftware.com/articles/2025/1/5.html

security add-generic-password -a dummy -C note -D "secure note" -T "" -s "your note name"

You can still create new secure note, but it is not recommended.

Apple recommends moving these to Notes in locked mode. But I don’t like this solution. I usually leave my Notes app open on my Mac as scrapbook. And whilst FaceID might not be easy to “hack” technically, it is not that hard to force someone to look at the phone.