The workflow is designed to allow you to customise it fairly heavily.
You can add your own scripts to provide new URL actions that the workflow will show in its action lists. You can also assign Hotkeys to scripts and bookmarklets to execute scripts more quickly from tab or bookmark lists.
It is also possible to add your own Hotkeys or keywords to the workflow to directly run scripts without having to use the default UI.
NOTE: Any custom elements you add will be removed when you update the workflow. Don't forget to back them up before updating!
See the scripting docs for info on how to call the alfred-firefox executable directly.