In S8E3 of Game of Thrones, Jon unsuccessfully tries to stop Daenerys from leaving the mountain they are perched on as they watch the Dothraki get chewed up by the undead hordes. In the "Inside the Episode" after, one of the writers states that "the plan" begins to unravel when Daenerys takes off on Drogon.
Was this plan ever elaborated or alluded to? What were Daenerys and Jon waiting for?