This feature is live in Android 16 DP1 and should arrive in the stable release unless Google removes it.

It might be tempting to have all your notifications show up on the lock screen so you don't have to unlock your device to see them. However, doing so exposes your sensitive information to potential threats, such as thieves who could easily access your notifications if they steal your device. Even worse, if notifications containing two-factor authentication codes appear on the lock screen, someone could see them and potentially get access to your online accounts. Fortunately, Google is working on a new feature in Android 16 that protects your most sensitive notifications containing two-factor authentication codes.