I have a scenario where I have 3 artboards, along those artboards I have three shapes as a repeating grid; I fill those shapes with images, and now want to place that grid atop an artboard by not part of it. This may seem strange, but in this example I'm recreating a screen, so essentially want to have those three images as transparent to work as guides.

Currently any object placed atop an artboard becomes part of that artboard, so in my case that repeating grid of images is hidden outside the first artboard.