Change the Event page's displayed name using the WP the_title() filter. Requires ee3.5 or greater, but not compatible with EE4.

custom_event_name.php

<?php
/*
Plugin Name: Custom Espresso Event page nice names
Plugin URI: http://gist.github.com/
Description: Changes the page name to be the event name. Requires Event Espresso 3.1.35.P or higher.
Version: 1.0
Author: Josh Feck
License: GPLv2
*/
 

/**
 * Filters the_title() to display the event's name instead of the page's title.
 * 
 *
 */
function ee_event_page_nice_name( $title ) {
 
	// only do stuff if espresso_get_event exists
	if ( function_exists('espresso_get_event') ) {
		global $this_event_id;
 
		if (isset($this_event_id) && !empty($this_event_id)){
			$event_id = $this_event_id;
		}
		
		if ( empty( $event_id ) ) return $title ; //get out this isn't an ee page.
		
		$event = espresso_get_event( $event_id );
 
		//one more sanity check
		if ( empty( $event ) || !in_the_loop() ) return $title; //get out!
 
		if ( $event_id ) { // if there's an event id...do stuff...
			$event = espresso_get_event( $event_id );
 			
			$title = '';
	
			// Add the site name.
      
			$title = "$event->event_name";
	
			return $title;
 
		}
	}
}
 
add_action( 'action_hook_espresso_social_display_buttons', 'ee_mod_page_name');
 
function ee_mod_page_name() {
	add_filter( 'the_title', 'ee_event_page_nice_name', 10, 2 );
}