How to programmatically configure Chrome extension through Selenium WebDriver

Since you mention that the problem is mainly on remote and I notice you are using SauceLabs, have you check this article from them?

https://support.saucelabs.com/customer/en/portal/articles/2200902-creating-custom-firefox-profiles-and-chrome-instances-for-your-automated-testing

Installing an Firefox Extension such as Modify Headers(You would need download the .xpi file on your machine first):DesiredCapabilities caps = new DesiredCapabilities();FirefoxProfile profile = new FirefoxProfile();profile.addExtension(new File("path\of\Modify Headers xpi file"));profile.setPreference("general.useragent.override", "UA-STRING");profile.setPreference("extensions.modify_headers.currentVersion", "0.7.1.1-signed");profile.setPreference("modifyheaders.headers.count", 1);profile.setPreference("modifyheaders.headers.action0", "Add");profile.setPreference("modifyheaders.headers.name0", "X-Forwarded-For");profile.setPreference("modifyheaders.headers.value0", "161.76.79.1");profile.setPreference("modifyheaders.headers.enabled0", true);profile.setPreference("modifyheaders.config.active", true);profile.setPreference("modifyheaders.config.alwaysOn", true);profile.setPreference("modifyheaders.config.start", true);caps.setCapability(FirefoxDriver.PROFILE, profile);NOTE: If you trying to do the same using C#, you would need to use the ToBase64String() method.

    public void AddHeaderChrome()    {    ChromeOptions  options = new ChromeOptions();    options.addExtensions(new File("C:\\Downloads\\ModHeader_v2.0.9.crx"));     DesiredCapabilities capabilities = DesiredCapabilities.internetExplorer();    capabilities.setCapability(CapabilityType.options);    // launch the browser    WebDriver driver = new ChromeDriver(options);    String HeadersName[]=new String[10];    String HeadersValue[]=new String[10];;    int length;    if(ConfigDetails.HeadersName.contains(","))    {    HeadersName=ConfigDetails.HeadersName.split(",");    HeadersValue=ConfigDetails.HeadersValue.split(",");    length=HeadersName.length;    }    else    {       HeadersName[0]=ConfigDetails.HeadersName;        HeadersValue[0]=ConfigDetails.HeadersValue;       length=1;    }       int field_no=1;    for(int i=0;i<length;i++)    {    driver.get("chrome-extension://idgpnmonknjnojddfkpgkljpfnnfcklj/popup.html");    driver.findElement(By.xpath("//input[@id='fl-input-"+field_no+"']")).sendKeys(HeadersName[i]);    driver.findElement(By.xpath("//input[@id='fl-input-"+(field_no+1)+"']")).sendKeys(HeadersValue[i]);    field_no+=2    }

An extension on Chrome has a constant unique ID.

You can use selenium web driver navigate to chrome-extension://<EXTENSION_UUIF>/options.html, here options.html is the preference page you defined.

Then execute a snippet of script to change the settings that stored in chrome.storage.local.