Now that Firefox 2 has been released and the Modify Headers upgrade to support it completed, I have finally got round to fixing an usability issue that has been irritating me for a while.
Previously when clicking the Edit button, the header name and value would be placed in the appropriate text box, but the action select would not change, it would always be stuck on Add. Now, this has been resolved.
Firefox auto-update will handle this for most people, but if you don’t have Modify Headers, go install it from Mozilla Update.