Here is how to turn on and re-enable the link manager in WordPress.
As of Version 3.5, the Links Manager and blogroll are hidden for new installs and any existing WordPress installs that do not have any links.
You might think you need to do something like this:
But actually the plugin that re-enables the link manager is but a single line of PHP code:
add_filter( 'pre_option_link_manager_enabled', '__return_true' );
Which brings back the familiar link manager (