In the documentation is says
If you don’t know the secret key for your device
Secret keys cannot be recovered if lost. Make sure to save any Device ID and Secret key that’s provided when adding an Arduino UNO R4 WiFi, Arduino Nano ESP32, or a 3rd party device (ESP32 and ESP8266). If you’ve lost your secret key, you can generate a new key by deleting the device, then adding it again.
I deleted the device and when creating a new device the Secret Key is not shown unless I do a manual configuration. Is this possible when selecting "Arduino Board" when setting up the new device?