Need a backup or a quick variation? Duplicate a layer — it is the fastest way to iterate and test ideas.
Steps to duplicate layers
Select the layer you want to copy in the timeline.

Go to Edit → Duplicate (or just press Ctrl+D on Windows / Command+D on Mac) and you get an instant copy in the same spot.

Move the copy in time or position to create quick repeats or stacked effects. It’s that simple.

One more thing
Duplicate first, then swap the source — Alt/Option-drag a new clip from your Project panel onto the copy — to preserve all the transforms and effects you already have set up.
Related how-tos
How to rename layers in After Effects
How to move layers up and down in the stack in After Effects
How to hide and show layers quickly in After Effects
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