It's a ground up Cocoa rewrite of the host app Paul, many things are likely to have changed. In my case, the assumption is based on educated guesswork. FxScript is FCP's aging Carbon based effect scripting language (many of the calls are just exposing underlying Carbon functions of the same name) and not suprisingly its seen no development for a very very long time (as opposed to the more modern FxPlug framework which Apple have been using themselves to author new built-in effects since FCP5). Seems to me it would frankly be rather surprising if Apple continued to support it in FCP X, my guess is that it will likely have been deprecated. Hence the requests here for clarification.