How do I easily find and delete media that I did not use in iMovie 10.0.9?

Hello! Please accept my apologies if this question has already been asked and answered, but I haven't been able to find the information I need.

I have a lot of videos and still shots imported into iMovie. But I am running out of room! Is there an easy way to find/delete any unused clips/pictures out of my iMovie library?? In other words, can iMovie identify clips that are not attached to a (completed or in-progress) movie project and get them outta there?

Thanks so much!