Since [`max_result_window` is a dynamic index setting](https://www.elastic.co/guide/en/elasticsearch/reference/current/index-modules.html#dynamic-index-settings), you can update it with

```c#
var client = new ElasticClient();

var updateIndexSettingsResponse = client.UpdateIndexSettings("index_name", u => u
    .IndexSettings(di => di
        .Setting("index.max_result_window", 20000)
    )
);
```

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