The Complete Onboarding and Go Live page is at /admin/clientgolive. Reach it from the wizard's Continue to Go Live checklist button, or by typing the address. It needs an admin role or a Sprwt onboarder session (the page redirects home for anyone else). Once your site has been switched to its live domain by Sprwt, the page redirects straight to the dashboard instead, because the go-live work is done.