On MacOS, require TouchID/password authentication to both unlock the app and after some inactivity period.
Bear and Day One offer this functionality. Would be super useful to have in Workflowy.
Bear’s post: Bear 1.7 is here with note Encryption, Bear Lock, Live Note Links, and more!
Day One’s posts: Passcode & Biometrics in-app options in Day One for macOS and End-to-End Encryption FAQ .