I work with a lot of network storage and video world stuff. While most in the editorial world prefer FinalCut, Avid, Adobe and other tools for video management, I do see the occasional task done in iMovie. By default, iMovie doesn’t support using assets stored on network volumes. However, you can make it. To do so, just use defaults to write com.apple.iMovieApp with a boolean allowNV key marked as true:
defaults write com.apple.iMovieApp allowNV -bool TRUE
