Beginning in app release 3.1.11 Biometrics can be turned on in the settings portion of the My Leviton app. The example is using iOS and Fingerprint, the process is similar for Face ID.
Choose menu in the lower right corner:
Choose Settings:
Choose Biometric Login:
Choose Use Fingerprint or Face ID:
Return to the menu and Logout:
At the Login screen select Use Fingerprint or Face ID and enter your My Levtion email and password:
Choose Login with Fingerprint or Face ID:
Scan your fingerprint or Face ID to log in: