How to create a custom filter in CiviCRM manage event page?
I would create replica of Manage event using Drupal views with same columns and filters as of Manage event screen. 

If you still want to use the same screen then use pageRun hook to manipulate results by generating query and creating results and assigning to template

$page-&gt;assign('rows', $manageEvent);


Cheers

Pradeep