Yes. If you use the Firefox Developer Tools, click the Network tab and select the request that you want to edit, there is an Edit & Resend button in the header details.

For more information, see Network Request Details.

Hope this helps.

It only shows header info for the single request. But I want to add the specified header to the default display layout like Status, Method, Domain, etc. Then I can easily find or sort out the same type of requests, for example x-cache. Thanks.

You can right-click the header bar to select what to display. You can also add items from the HTTP response headers.

• https://developer.mozilla.org/en-US/Tools/Network_Monitor