How do I separate iMovie projects for backup and sharing?

iMovie does support multiple libraries.

How to create a new library:

  1. Launch iMovie
  2. Click on "File"
  3. Hover on "Open library"
  4. Click on "New…"
  5. Select where you want that library to be stored.

Now you got an extra library to which you can move any iMovie project, and then you'll be able to share what need to...