Precomposing
layers places them in a new composition (sometimes called a precomposition),
which replaces the layers in the original composition. Precomposing
a single layer is useful for adding transform properties to a layer
and influencing the order in which elements of a composition are
rendered.
Select the layers in the Timeline panel, and choose
Layer > Pre-compose or press Ctrl+Shift+C (Windows)
or Command+Shift+C (Mac OS).
Select one of the following:
Leave All Attributes
In
Leaves
the properties and keyframes of the precomposed layer in the original
composition, applied to the new layer that represents the precomposition.
The frame size of the new composition is the same as the size of
the selected layer. This option is not available when you select
more than one layer, a text layer, or a shape layer.
Move All Attributes Into The New Composition
Moves the properties and keyframes of the
precomposed layers one level further from the root composition in
the composition hierarchy. When you use this option, changes you applied
to the properties of the layers remain with the individual layers
within the precomposition. The frame size of the new composition
is the same as that of the original composition.
