Computer Configuration > Administrative Templates > Google Chrome - Default Settings (users can override) > Default search provider
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HKLM\Software\Policies\Google\Chrome\Recommended
If DefaultSearchProviderEnabled is on, then setting DefaultSearchProviderSuggestURLPostParams specifies the parameters during suggestion search with POST. It consists of comma-separated, name-value pairs. If a value is a template parameter, such as '{searchTerms}', real search terms data replaces it. Leaving DefaultSearchProviderSuggestURLPostParams unset unset means suggest search requests are sent using the GET method. Example value: q={searchTerms},ie=utf-8,oe=utf-8