iMovie

If you’re looking for iMovie Theater in iMovie on Mac
Sharing to iMovie Theater is no longer supported. If you’ve shared movies or trailers to the Theater in previous iMovie versions, you can still view, share, and delete them. To continue to view movies or trailers you’ve shared to the Theater on all your devices, import the movies or trailers into Photos and make sure iCloud Photos is turned on. After you’ve imported all your movies and trailers into Photos, you should delete them from iMovie Theater.