ZachThis short guide will show you how to rename your library in iMovie. This is especially useful if you maintain multiple iMovie libraries -- for example, one on an internal and one on an external hard drive.
Double-click your iMovie Library.imovielibrary file to open it in iMovie.
In the sidebar under the LIBRARIES heading, click your library name once (the default library name is iMovie Library).
Wait a few seconds and then click it a second time. You will now be able to edit the name. Type the new, desired name (for example, External iMovie Library) and press your Enter key.
You're all done!