Example of custom My Account endpoint.

custom-my-account-endpoint.php

<?php
class My_Custom_My_Account_Endpoint {

	/**
	 * Custom endpoint name.
	 *
	 * @var string
	 */
	public static $endpoint = 'my-custom-endpoint';

	/**
	 * Plugin actions.
	 */
	public function __construct() {
		// Actions used to insert a new endpoint in the WordPress.
		add_action( 'init', array( $this, 'add_endpoints' ) );
		add_filter( 'woocommerce_get_query_vars', array( $this, 'get_query_vars' ), 0 );

		// Change the My Accout page title.
		add_filter( 'the_title', array( $this, 'endpoint_title' ) );

		// Insering your new tab/page into the My Account page.
		add_filter( 'woocommerce_account_menu_items', array( $this, 'new_menu_items' ) );
		add_action( 'woocommerce_account_' . self::$endpoint .  '_endpoint', array( $this, 'endpoint_content' ) );
	}

	/**
	 * Register new endpoint to use inside My Account page.
	 *
	 * @see https://developer.wordpress.org/reference/functions/add_rewrite_endpoint/
	 */
	public function add_endpoints() {
		add_rewrite_endpoint( self::$endpoint, EP_ROOT | EP_PAGES );
	}

	/**
	 * Add new query var.
	 *
	 * @param array $vars
	 * @return array
	 */
	public function get_query_vars( $vars ) {
		$vars[ self::$endpoint ] = self::$endpoint;

		return $vars;
	}

	/**
	 * Set endpoint title.
	 *
	 * @param string $title
	 * @return string
	 */
	public function endpoint_title( $title ) {
		global $wp_query;

		$is_endpoint = isset( $wp_query->query_vars[ self::$endpoint ] );

		if ( $is_endpoint && ! is_admin() && is_main_query() && in_the_loop() && is_account_page() ) {
			// New page title.
			$title = __( 'My Custom Endpoint', 'woocommerce' );

			remove_filter( 'the_title', array( $this, 'endpoint_title' ) );
		}

		return $title;
	}

	/**
	 * Insert the new endpoint into the My Account menu.
	 *
	 * @param array $items
	 * @return array
	 */
	public function new_menu_items( $items ) {
		// Remove the logout menu item.
		$logout = $items['customer-logout'];
		unset( $items['customer-logout'] );

		// Insert your custom endpoint.
		$items[ self::$endpoint ] = __( 'My Custom Endpoint', 'woocommerce' );

		// Insert back the logout item.
		$items['customer-logout'] = $logout;

		return $items;
	}

	/**
	 * Endpoint HTML content.
	 */
	public function endpoint_content() {
		echo '<p>Hello World!</p>';
		// You can load a template here with wc_get_template( 'myaccount/my-custom-endpoint.php' );
	}

	/**
	 * Plugin install action.
	 * Flush rewrite rules to make our custom endpoint available.
	 */
	public static function install() {
		flush_rewrite_rules();
	}
}

new My_Custom_My_Account_Endpoint();

// Flush rewrite rules on plugin activation.
register_activation_hook( __FILE__, array( 'My_Custom_My_Account_Endpoint', 'install' ) );

Well done ! my plugin is ok. I was in trouble, however the solution was to set priority for this action ;
add_action( 'woocommerce_account_' . self::$endpoint . '_endpoint', array( 'My_Endpoint', 'function_content' ),10 );

Gosh thanks for the code!
You have to re-save your permalink to make it work. However mine looks like this:

Any idea which part of the code are making this?

Great piece of code! Thank you so much for this. One question: How do I add two custom endpoints?

@claudiosanches This example worked.

But I have another problem. I choose My-account as my static root page. The new point show 404 or post page.
Can you suggest away to solve?

Perfect solution with the update by @coldfusion411
I just wanted to add something to the people who are new @WP development:
If you want to make it a plugin, the code should start with:

/*
Plugin Name: My Plugin
Plugin URI: https://www.mydomain.com/my-plugin
description: My description
Version: 1.0
Author: My Name
Author URI: https://www.mydomain.com/about-me
License: GPL2
*/

Great job! How i can change this code to add more than one endpoint page?

This is helpful. Also this is also helpful

However, as @MikeWP says, how to add more than one custom endpoints? I would also like to know this.

When I use this code I cannot use 'my-custom-endpoint' with the function "is_wc_endpoint_url()". Whereas "is_wc_endpoint_url()" works with the core WC endpoints to return a true value (e.g. "is_wc_endpoint_url('orders')" or "is_wc_endpoint_url('edit-address')"), the function returns empty (or false/"0" Boolean) when using 'my-custom-endpoint'. I've also tried other custom endpoints with the same problem.

Does anyone know what additional coding is required of the custom endpoints to be compatible with the "is_wc_endpoint_url" function? I'd really like to be able to utilize this function for conditional logic on custom tabs. Thanks!

Above endpoint is working fine. But now I want to open a new page as woo order listing is working. Please check this link https://nimb.ws/1fn4wa

I want to list all offers and also I want to shoe each offer single details in the my account section. Please advice.

Does not work with conditional

is_wc_endpoint_url('my-custom-endpoint')
returns false

UPD
add this to __construct
add_filter( 'woocommerce_get_query_vars', [ $this, 'add_query_vars' ], 0 );

and change add_query_vars()
to
public function add_query_vars( $vars ) {
$vars[self::$endpoint] = self::$endpoint;

	return $vars;
}