How to edit .xpi add-on File.
Download .xpi file to your system. Go to your system folder properties.
Folder Options > View > un check to "File Extensions for knows file types"
Now you can see extension to every file. Like nodofollow.xpi
You need to change extension from xpi to zip like nodofollow.xpi to nodofollow.zip
Now you can see add-on parts. You can edit, modify, delete add-on parts.
