Answered: Create the qa-lang-....php file for the template

I don't know it's possible or not, But I'm using Private Variables inside my Theme, instead of looking the whole theme to find all the custom text I've used in theme now I can find all of them in top of my theme, I've declared them inside this class.

qa_html_theme extends qa_html_theme_base

You can call them wherever you need

$this->name_of_variable