I shoot a lot of storm timelapses with my Nikon D850 and Z6 using the internal intervalometer. The interval is typically between 1 and 3 seconds. I set up the shot and much of the time the storm will move from one side of the frame to the other. The problem I have is that I can’t really tell when the “subject” of the shot has moved out of the frame since the LCD is blacked out during the timelapse. I have seen other brands (specifically, Sony) that don’t black out the LCD so it’s easy to see when the clouds move out of the shot. Do you know if there is any way to see a preview during a timelapse on a Nikon?

You need to use an external intervalometer. The internal just has a dark time that's way too long.
That's the main reason why I developed the LRT PRO Timer - it's the intervalometer that offers the shortest possible dark times.
See my video (for a comparison) and explanations on https://lrtimelapse.com/lrtpt/