The popup window enabled at civicrm/admin/setting/debug?reset=1 contains only the top level Smarty template variables. How can I see the variables for a lower level included Smarty template?
There is only one smarty template object and hence only one scope. Hence the variables that are displayed at the top level include the variables that are displayed at all levels.
You can optionally rename a variable and/or send in a constant to the included templates, but besides that its all one scope. You should think of template inclusion more as a macro rather than a function call.