With all due respect, I believe you are missing the point. I totally understand that Parallels 19 uses your Microsoft account password stored in your Keychain to log you into Windows. However, the problem is that the Windows login screen defaults to requiring you to type a password. In order to utilize the TouchID feature, one must click the fingerprint icon under Sign-In options, which seems to be an unnecessary additional step. We are asking if there is a way for the Windows login screen to default to the finger scan options to eliminate the extra mouse click. The knowledge base for Parallels 19 even states:
Starting with Parallels Desktop 19, by popular demand, we are introducing the ability to use your Mac fingerprint sensor to log into a Windows virtual machine.
Mac Keychain and trigger the input when required by the system for logging in. The password is stored in a secured keychain, access to which is protected by your Mac administrative Touch ID. It cannot be viewed but can be copied or removed from the Keychain, provided the user possesses the administrative credentials.
Note: this feature doesn't imply support for Windows Hello as a sign-in option via TouchID.

You will need to enter the password for your account once, after which it will be stored in the Keychain, and subsequent logins will be performed by using your TouchID scanner, and you will be prompted to use it instead on every system start:

Once you see the Touch ID prompt, touch your Mac's fingerprint scanner, and you will be logged into Windows.
It seems to suggest that once you login with your password one last time, you will be prompted with TouchID going forward. This is NOT what is happening.
Thank you.