These are all of the available Smarty class variables. You can access them directly, or use the corresponding setter/getter methods.
All class variables have magic setter/getter methods available. setter/getter methods are camelCaseFormat, unlike the variable itself. So for example, you can set and get the $smarty->template_dir variable with $smarty->setTemplateDir($dir) and $dir = $smarty->getTemplateDir() respectively.
Changing settings by templatesection for how to change Smarty class variables for individual templates.