As I understand it, the narrator must currently designate all potential cards for pick-up at the beginning of a scene. I would love for this option to still be available to the narrator in the middle of the scene - say a player decides to make their part in the scene about examining someone's file.

The narrator would not have known this ahead of time and thus would not have created an asset card for it, and as the game stands now (as I understand it), cannot do so while still in the middle of a scene. Giving the narrator the same option they have at the start of a scene at all times would be very helpful in such a situation and would relieve pressure on the narrator at the beginning of the scene.