Different slides in different windows?

[AustenLamacraft]

I admit this is a rather niche use case (maybe). In technical lectures in maths or physics using blackboards or whiteboards, it's convenient to have multiple boards visible at once, so that in the course of a long derivation you can refer the audience back to earlier material without losing sight of where you are.

Where I lecture at the moment, there are multple screens and I would like to be able to do the same thing with a reveal slideshow: to display multiple browser windows, one on each screen, so that one display shows the current slide, another the previous slide, etc. This would only really be practical if when one window is moved to the next slide, the other windows move along accordingly.

I've no idea how this would be done in practice, although I did just read about the Broadcast Channel API, which sounds suitable.