Apple Motion 5.1.1 - Manual (Page 263)

Chapter 8 Timeline 263
Add an object using Overwrite edit
The Overwrite drop menu option deletes the existing layer, overwriting it with your new layer.
After Overwrite edit
Before
If the new layer is shorter than the one currently in the group, the Overwrite option splits the
duration of the existing layer and deletes only the frames where the new layer appears.
After Overwrite edit with shorter clip
Before
Overwrite a layer
1 Drag an item from the File Browser, Library, or Media list into the Timeline track area.
As you drag, a tooltip appears, indicating the frame number where you are located.
2 Drag to the frame where you want the new layer to start, holding down the mouse button until
the drop menu appears.
3 Choose Overwrite from the drop menu.
67% resize factor