How to add subheading in Orders Page
In the url, user/%user/orders/%commerce_order (or user/1/orders/1) also known as the order details page, how can I add a subheading? All I know is how to change the title (implement hook_menu_alter, change the title callback, etc). But I'm having trouble figuring out how to add a subheading in the page. I tried tracing the code and figure out how the page is generated but I can't figure it out. How is the page generated or what hook/s should I implement to achieve this?