The WordPress default menu functions offers a great many features and options, some of which can be difficult to modify without delving into the code itself. For example, if a theme author chooses to turn “on” the “show_home” option in the default menus such as Twenty Twelve does in its functions.php template file with this … ∞
Expand the wp_nav_menu() function by adding menu items to the output with the add_filter() function.
Upgrading from wp_page_menu() to wp_nav_menu() may be as easy as a simple find and replace operation.
Examples of adding a home page link to a WordPress theme with code that can be easily copied and pasted.