void replaceRouteBelow({Route anchorRoute, Route newRoute })

Replaces a route that is not currently visible with a new route.

The route to be removed is the one below the given anchorRoute. That route must not be the first route in the history.

In every other way, this acts the same as replace.

Source 

void replaceRouteBelow({ Route<dynamic> anchorRoute, Route<dynamic> newRoute }) {
  assert(anchorRoute != null);
  assert(anchorRoute._navigator == this);
  assert(_history.indexOf(anchorRoute) > 0);
  replace(oldRoute: _history[_history.indexOf(anchorRoute)-1], newRoute: newRoute);
}