At the moment you can’t add columns from Sitecake UI. You need to create columns in you HTML file by yourself.
Sitecake has been developed as a CMS for editing existing websites, for quick changes over the existing content. We have planned custom HTML snippets that can be prepared by template designer and pulled down from the toolbar. (eg. multiple column layouts). It will be put on feature voting by users to determine the priority among other features.
Syntax hightlight? Hmm, either you create css styles and apply them through Sitecake toolbar style option.
https://github.com/sitecake/sitecake/wiki/User-Styles
or you add some js that will do the auto highlighting for you.
(or write raw HTML through Sitecake raw HTML module, but that is not optimal)