On a slightly smaller scale we've sismic imagery (think like a sonogram) of a lot of the near surface plumbing on the big island so that cover Kilauea, Manua Loa, and a few other features. If you read about the 2018 eruption of Kilauea you'll see that in action as it's all about a loss of pressure in the system.

I'd also add that the hotspot didn't just make the modern Hawaiian Islands. There's a whole chain of eroded sea mounts that used to be other islands! And the direction they go in is in the direction the Pacific plates is moving. And this is a trait we see in other hot spit volcanos. Since the souce of the heat is from the mantle it doesn't move, but the plates still move over it.