The Relationship Between Source Media and Image Layers
Every media file you add to your project places corresponding source media in the Media
list. This means that if you import the same file into your project five times, five identical
source media items are added in the Media list.
However, if you duplicate a layer in the Layers list, you create an instance of the layer but
not a new source item in the Media list. Rather, both duplicate layers are linked to a single
source item in the Media list.
Creating and Managing Projects
By default, media added to your project is managed by Motion. If you delete a layer from
the Canvas or Layers list, the source media is removed from the Media list. You can turn
off this media management feature in the General pane of Motion Preferences. For more