Firefox for Android allows you to register WebAuthn credentials and save them to "this device". You can test this at https://webauthn.io/ . However, I have not been able to find a way to view or remove those credentials saved to "this device". What is the location of where those credentials are saved, and how do I remove them? Note that these credentials are not visible in Settings > Logins and passwords > Saved logins. That section seems to only be for saved passwords and does not include WebAuthn credentials.