Since version 1.9.2, the secondary title of a post can also be accessed through the following shortcode:
When placed into the content area of a post, page or custom post type, this shortcode will be replaced with the corresponding secondary title. The shortcode can be extended through its parameters.
post_id(int): The ID of the targeted post. Default: Current post ID.
allow_html(bool): Renders HTML code used in the secondary title. Default:
[secondary_title allow_html="false" post_id="31"]
[secondary_title post_id=117](Shows the secondary title of the post with the ID 117)