When logged in you get access to more options on adding more layers and shim paper.
New layer: Add new layers if needed.
Duplicate top layer: If you’ve added some custom changes to your top layer, you can add more in the same pattern. All you have to do is choose what stacking pattern this new layer should have, copied, rotated, mirrored vertically or mirrored horizontally.
Shim Paper: A lot of projects requires a shim paper. By clicing this button, a shim paper will automatically be added over the top layer. Read more about shim paper here.