I have it disabled, but not quite sure, which settings, try this: EDIT: OK, so after some testing, actually you have to enable Quit hours to get rid of this pesky notification. reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Notifications\Settings" /v "NOC_GLOBAL_SETTING_TOASTS_ENABLED" /t REG_DWORD /d "0" /f
Sounds a tad excessive - looks that disables all toasts... Though if that's what you want, then I can't deny that's a solution Personally, I'd just bite the bullet, and turn off all of the Security and Maintenance notifications but keep the Security Centre service running
on RS1 you can deactivate it in the Settings app -> System -> Notifications & actions -> Get notifications from these senders -> Security and Maintenance -> Off.