Just export your project as .fcpxml (File > Export XML), drag it onto the dock icon, select the clip you’d like to export, and it’ll create and open a new Motion project, setup with the right length, clip, and frame rate. It’s not perfect, but it saves a lot of time setting up projects and copying information by hand.
And here's a comment from the developer in the original linked article:
"What I tend to do is render a movie, copy the old clip in FCPX, drop on the new clip to replace and audition, and then paste effects from the old clip, so you get your audio/etc. changes back."
Principal & Designer at Keen Live
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