WordPress at a glance
action is not described

manage_sites_custom_column action-hook . WP 3.1.0

Fires for each registered custom column in the Sites list table.

Usage

add_action( 'manage_sites_custom_column', 'action_function_name_1147', 10, 2 );
function action_function_name_1147( $column_name, $blog_id ){
	// action...
}
$column_name(string)
The name of the column to display.
$blog_id(int)
The site ID.

Where the hook is called

WP_MS_Sites_List_Table::column_default()
wp-admin/includes/class-wp-ms-sites-list-table.php 448
do_action( 'manage_sites_custom_column', $column_name, $blog['blog_id'] );

Where the hook is used (in WP core)

Does not used.