MACROMEDIA STUDIO 8-EXPLORING STUDIO 8 Manual page 70

70 Studio Basics
You can also organize and manage layers by creating layer folders and
placing layers in them. You can expand or collapse layer folders in the
Timeline without affecting what you see on the Stage. It's a good idea to
use separate layers or folders for sound files, ActionScript, frame labels,
and frame comments. This helps you find these items quickly when you
need to edit them.
In addition, you can use special guide layers to make drawing and editing
easier, and mask layers to help you create sophisticated effects.
For an interactive introduction to working with layers in Flash, select
Help > Flash Tutorials > Basic Tasks > Work with Layers.
Creating layers and layer folders
When you create a new layer or folder, it appears above the selected layer.
The newly added layer becomes the active layer.
To create a layer, do one of the following:
Click the Insert Layer button at the bottom of the Timeline.
Select Insert > Timeline > Layer.
Right-click (Windows) or Control-click (Macintosh) a layer name in
the Timeline and select Insert Layer from the context menu.
To create a layer folder, do one of the following:
Select a layer or folder in the Timeline, and then select Insert >
Timeline > Layer Folder.
Right-click (Windows) or Control-click (Macintosh) a layer name in
the Timeline, and then select Insert Folder from the context menu.
The new folder appears above the layer or folder you selected.
Viewing layers and layer folders
As you work, you may want to show or hide layers or folders. A red X next
to the name of a layer or folder in the Timeline indicates that it is hidden.
When you publish a Flash SWF file, any layers that were hidden in the
FLA document are preserved and visible in the SWF file.
To help you distinguish which layer an object belongs to, you can display
all objects on a layer as colored outlines. You can change the outline color
used by each layer.