I want to split an atomic tree into different parts. The routine tree-split does not quite work as I expected. What must I do if I not only want to split the atomic tree but want to have both parts displayed again? I want to later modify only one of them by replacing it with a <my-macro|it>. I tried (tree-split my-path 1 1) on a <section|The Theory of Ordinals> and got <section|T|he Theory of Ordinals> and this is diplayed as a T. Is there a higher level routine?