The extension adds a context menu to BurpSuite that allows you to copy multiple requests as Javascript's XmlHttpRequest, which simplifies PoC development when exploiting XSS.
- download the latest JAR from releases or build manually
- add JAR to burpsuite using tabs: "Extender" -> "Extensions" -> "Add"
- select one request from any tab or a few requests in "Proxy" -> "HTTP history" tab
- invoke context menu and select "Copy as XMLHttpRequest"