How to modify core files

• Search in files for a key term. The more specific, the better. "Twitter" rather than "twitter", with "match case" selected.
• Browse through the most promising files. E.g., "\wordpress\wp-content\themes\taskerr\theme-framework\kernel\social.php".

APP_Social_Networks::register_network( 'facebook', array(
	'title' => __( 'Facebook', APP_TD ),
) );

APP_Social_Networks::register_network( 'twitter', array(
	'title' => __( 'Twitter', APP_TD ),
) );

APP_Social_Networks::register_network( 'linkedin', array(
	'title' => __( 'LinkedIn', APP_TD ),
	'user_url' => 'https://linkedin.com/in/%s/'
) );

APP_Social_Networks::register_network( 'google-plus', array(
	'title' => __( 'Google+', APP_TD ),
	'base_url' => 'https://plus.google.com/',
	'user_url' => 'https://plus.google.com/%s/',
) );

APP_Social_Networks::register_network( 'youtube', array(
	'title' => __( 'YouTube', APP_TD ),
	'user_url' => 'https://youtube.com/user/%s/'
) );

APP_Social_Networks::register_network( 'instagram', array(
	'title' => __( 'Instagram', APP_TD ),
) );

APP_Social_Networks::register_network( 'pinterest', array(
	'title' => __( 'Pinterest', APP_TD ),
) );

APP_Social_Networks::register_network( 'github', array(
	'title' => __( 'Github', APP_TD ),
) );

APP_Social_Networks::register_network( 'path', array(
	'title' => __( 'Path', APP_TD ),
) );

APP_Social_Networks::register_network( 'vimeo', array(
	'title' => __( 'Vimeo', APP_TD ),
) );

APP_Social_Networks::register_network( 'flickr', array(
	'title' => __( 'Flickr', APP_TD ),
) );

APP_Social_Networks::register_network( 'picasa', array(
	'title' => __( 'Picasa', APP_TD ),
	'base_url' => 'https://picasaweb.google.com/',
	'user_url' => 'https://picasaweb.google.com/%s/',
) );

APP_Social_Networks::register_network( 'foursquare', array(
	'title' => __( 'Foursquare', APP_TD ),
) );

APP_Social_Networks::register_network( 'wordpress', array(
	'title' => __( 'WordPress', APP_TD ),
	'user_url' => 'https://%s.wordpress.com/'

• This is clearly a LOT longer list than appears on the registration form. There must be a place in the Dashboard or in the code that controls which of these appear on that form.
• This provides another search term: "APP_Social_Networks"