And I think the option to disable the flashing light when bluetooth is connected is under that same key, except for the last part which should be: {A877D65D-239C-47a7-9304-0D347F580408}
Add a "Default" string, value "Bluetooth Connection" and then in the 'Sounds & Notifications' section of Control Panel change the options around for "Bluetooth Connection" notifications and see if the light stop blinking when you change that setting so that the light doesn't blink.
I don't have bluetooth, let alone built in bluetooth, so I don't know if that is it or not. All I know is that that key plays the wav "online" and blinks the light for a duration of 3 minutes, according to the settings it shows in the registry. Don't know what that could be.