I'm trying to get this to work and was hoping you could share with me the file path you were using (was it in mysite/_config.php?) or did you use the MyLeftAndMainDecorator.php workaround famous here: http://open.silverstripe.org/ticket/4390?
Also can you include the entire code snippet, I'm trying this without success:
HtmlEditorConfig::get('cms')->setOption('template_templates','title[Title Here]|src[themes/mytheme/path/layout1.htm]|description[some description text]');
This gives me an error message, which is more than what i get if i do:
HtmlEditorConfig::get('cms')->setOptions(array('template_templates'=>array('title'=>'Title Here','src'=>'themes/mytheme/path/layout1.htm','description'=>'some description text');