Manifest Digital, a St. Louis digital creative agency, will move into the @4240 building in the Cortex innovation district, officials announced Thursday. Manifest will occupy a 16,751-square-foot space on the second floor of the @4240 building, and will neighbor the Cambridge Innovation Center. Terms of the deal were not made public. Dan Curran, a Manifest Digital partner, said the lease is for seven years. Manifest will move its 40 local employees from its current downtown office, on the third…