Preview functionality cleanup

I know, but I think when you have something like this it's nice to explicitly pass the argument so that if we get another parameter in the signature later then you can still use the same signature as currently to use the default window, but add the extra arg for example:

    def foo(content, window: windows.last, something: "else")

    foo("rob", something: "other")

Right? I kind of thing we should often be naming arguments but this might be over the top.