devtools.inspectedWindow.reload()

reloadOptions Optional

object. Options for the function, as follows:

ignoreCache Optional

boolean. If true, this makes the reload ignore the browser cache (as if the user had pressed Shift+Ctrl+R).

userAgent Optional

string. Set a custom user agent for the page. The string supplied here will be sent in the browser's User-Agent header, and will be returned by calls to navigator.userAgent made by scripts running in the page.

injectedScript Optional

string. Inject the given JavaScript expression into all frames in the page, before any other scripts.

Reload the inspected window, setting the user agent and injecting a script:

const reloadButton = document.querySelector("#reload-button");

reloadButton.addEventListener("click", () => {
  browser.devtools.inspectedWindow.reload({
    injectedScript:"alert(navigator.userAgent);",
    userAgent: "Not a real UA"
  });
});