I'm hoping this is currently being implemented in the new fluid engine as this seems to be broken 'again.' I tried using the workaround above (thank you!) and can see "Looking for sections built with our classic editor?" hyperlinked at the bottom of the page, but when I click it, it just takes me to the top of the page and there's no way to add a classic section. Maybe someone from Squarespace can reassure me/us this feature is coming back? It seems very basic. Thank you!