I've been editing a video in macbook and it's running out of space..
How do I move the data to a new computer so that I can continue editing the video?
I ran into this as well, the YouTube video iMovie: How to transfer iMovie Project Files Between Mac Computers and backing up iMovie files. helped.
Basically, you create a Library in iMovie, then copy the project into the Library.
I tested this up to the point where I saw it created a 200 MB iMovie file, I didn't test to make sure it imports and functions correctly.
See this video - How to Export an iMovie Project.