Selenium header

 Thread.Sleep(2000);//Wait the extension about page open 

driver.Close(); //Close about page
driver.SwitchTo().Window(driver.WindowHandles[0]);

driver.Navigate().GoToUrl("chrome-extension://idgpnmonknjnojddfkpgkljpfnnfcklj/popup.html");

driver.ExecuteScript("document.getElementsByClassName('mdc-text-field__input')[0].value = 'MY_HEADER';");
driver.ExecuteScript(" var evt = document.createEvent('HTMLEvents');evt.initEvent('input', false, true);document.getElementsByClassName('mdc-text-field__input')[0].dispatchEvent(evt);");

driver.ExecuteScript($"document.getElementsByClassName('mdc-text-field__input')[1].value = 'MY_VALUE';");
driver.ExecuteScript("document.getElementsByClassName('mdc-text-field__input')[1].dispatchEvent(new Event('change'));");
driver.ExecuteScript(" var evt = document.createEvent('HTMLEvents');evt.initEvent('input', false, true);document.getElementsByClassName('mdc-text-field__input')[1].dispatchEvent(evt);");