Just copy the layout.xml and the layout.uistate.xml
change the names of the files to whatever you want. (for example to layout2.xml and layout2.uistate.xml)
open the new layout2.xml and change the name of the layout in the third line:
<?xml version="1.0" encoding="utf-8" ?>
<c2layout>
<name>layout2</name>
open the project.caproj with the a text editor and add the following line:
(scroll to the end of the file to find this part.)
<layout-folder expanded="1">
<layout>layout.xml</layout>
<layout>layout2.xml</layout>
</layout-folder>