JxBrowser doesn't support Google Chrome extensions. Google Chrome extensions integrate with Google Chrome app UI such as tool bar, context menu, etc. So, it's expected that Chrome extension is running in Google Chrome.
JxBrowser doesn't integrate with Google Chrome app. It integrates only with web browser control that renders web content via Chromium engine. So, the library doesn't have Google Chrome UI required for extensions. This is why JxBrowser doesn't support extensions.