The triforium galleries on the chancel side (east of the crossing) Circular windows above ogival recesses on the outside. These were already in place along the sides (N&S) but not where the galleries turn the corner up against the transepts. This reveals the need to omit the lower arches on the last flying buttresses, which lie in the plane of the outer wall. Maybe a visibility switch would do the trick.
So while I’m here, might as well add the door that leads to a spiral stair (presumably) And while I’m at it there are a couple of doors on the outside that connect via short balustraded galleries to the “bridge” that crosses the Rose Window. This arrangement seems to be specific to the North transept. The connections on the South side surely exist, but are not expressed on the outside of the building. Why the difference? Good question.
That spiral stair also connects to the roof over the Triforium Galleries. Not stair object at present, just an open…