I don't think this is gonna get implemented, it's just not a feature that would be used a lot, apart from some gimmicky stuff (in regards to games that is, since Construct is a game engine first and foremost)
However, Construct does let you add javascript. It seems quite benign actually to add the functionality you want with a few lines of code.
developer.mozilla.org/en-US/docs/Web/API/Broadcast_Channel_API