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.
Add movies or trailers in iMovie Theater to Photos
In the iMovie app
on your Mac, choose Window > Go to Theater.Click the More Options button
below the movie or trailer you want to share, then click Copy to File.Navigate to where you want to save the movie or trailer, then click Save.
In Photos, choose File > Import.
Navigate to the location where you saved the movie or trailer, then click Review for Import.
To view your movie or trailer on all your devices, make sure iCloud Photos is turned on (choose Photos > Settings, click iCloud, then select iCloud Photos). For more information, see the Apple Support article Set up and use iCloud Photos.
Delete a movie or trailer from iMovie Theater
When you delete a movie or trailer in the Theater, you can choose whether to remove the movie or trailer only from iCloud or from iCloud, your Mac, and all of your devices. Your source project and related media aren’t deleted, which means you can edit the project again.
In the iMovie app
on your Mac, choose Window > Go to Theater.Click the More Options button
below the movie or trailer you want to delete, then click Delete.Click one of the following options:
Delete from iCloud: The movie or trailer is still available on your Mac but is removed from iCloud.
Delete Everywhere: The movie or trailer is removed from iCloud, your Mac, and all of your iOS and iPadOS devices.