There's this suit of useful little programs called Microsoft PowerToys, I always thought it should include a tool that allows you to quickly swap the contents of monitors around in multi-monitor setups.
e.g. move all open windows from monitor 1 to monitor 2 and vice-versa, while retaining their (approximate) position.
This may already be a thing, I haven't really checked.
That's only useful though if someone looking for this function also happens to be looking for a tiling window manager. I assume most people needing this don't want a tiling window manager.