[Professional Version Only] Open up the Layers panel to organize shells into different layers (maximum of 5). Shells in the upper layers will appear over shells in the lower layers where they overlap. Layer assignments are saved into and restored from UVL files, but will be lost when the mesh is exported to an OBJ file.

New 

Create a new layer at the bottom of the list. If any shells are picked, they will be moved into the new layer.

U 

Move the active layer up the list.

D 

Move the active layer down the list.

X 

Delete the active layer. Any shells in that layer will be moved into the top layer.

Move 

Move all picked shells into active layer.

The top layer is special, and contains all the undropped shells. Every other layer has five widgets:

Active 

Click the first toggle to make that the active (green) layer. Click an already active green toggle and all other layers are hidden. Collapsing or killing the Layers panel will make all layers/shells active.

Shells not in the active layer are tinted gray and behave as if they are locked. They can't be re-flattened, packed, cut, welded or edited in any other way. They can be moved, scaled and rotated with the Space-LMB/MMB/RMB actions, but stay put when the Move/Scale/Rotate tools are used.

Hide 

Arm/disarm the second toggle box to show/hide all shells in that layer.

Name 

Set the name of the layer.

Pick 

Click the gray button to pick all shells in that layer. Click again to unpick the shells. This button also displays the number of shells in that layer.

Ctrl-LMB click the gray button to toggle a row showing the number of UV coordinates (vertexes) and polygons in that layer.

Lock 

The final toggle box is used to completely lock a layer. Shells on this layer will be drawn only in wireframe, and they can't be edited in any way, unless that layer is currently the active layer.