I'm not sure this is the right application of an Overton Window. It is more like a negotiation tactic, based on an old style of negotiation.

For example, I'm trying to promote an alternative democracy on Medium. However it is not in the Overton window; it is still in the "unthinkable" stage.

So it is not cool not cool to talk about this democracy.

When it moves to "radical," then a few people will be interested in talking about it. When it reaches "popular," then social forces will lead to "policy."

But until then, we are stuck with a system that elected Donald Trump and renders his opposition impotent.