We should have a new session in ZK_Component_Development_Essentials for "Extends existing component",
and the document here should be "create a new mold for existing component".

http://books.zkoss.org/wiki/ZK_Component_Development_Essentials

----------

http://www.zkoss.org/forum/listComment/17073

That seems some user want to build customized mold.

It would be great if we could have a document ,
which only focus on the purpose for "build a new mold" , not a full component.

I searched the forum and found this question have been asked few times before ,
I am also thinking of the css customization of UHG project , I believe that's one of our user need.

http://www.zkoss.org/forum/listComment/11878
http://www.zkoss.org/forum/listComment/1370