Joost de Valk

Yoast

Allows you to easily find the custom fields (including hidden custom fields) and their values for a post, page or custom 
post type post.
Just go to Tools – Custom field finder, enter the post ID of any post and you’ll see all the custom fields. This includes 
the custom fields that start with an underscore ( _ ) that are normally hidden from the custom fields interface.

Custom field finder

Allows you to easily find the custom fields (including hidden custom fields) and their values for a post, page or custom post type post.

Faison

Add <a href="https://codex.wordpress.org/Navigation_Menus" rel="nofollow ugc">Navigation Menus</a> to <a href="https://wordpress.org/extend/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a> (ACF) with the Nav Menu Field plugin! This plugin adds the Nav Menu Field type to ACF (version 5 & 4), allowing you to select from the menus you create in the WordPress Admin backend to use on your website’s frontend.
Using ACF, you can set the Nav Menu Field to return the selected menu’s:
<ul>
<li>ID for lightweight coding,</li>
<li>Object for more involved programming, or</li>
<li>HTML (generated from <a href="https://codex.wordpress.org/Function_Reference/wp_nav_menu" rel="nofollow ugc">wp_nav_menu</a>) for quickly displaying a menu.</li>
</ul>
I created this plugin because I needed to display a secondary menu that changed depending on what page you’re on. Most of those pages were children of the same page, but then I had to throw a couple of Custom Post Types in there too. Because of the Custom Post Types, I couldn’t just grab the top most parent for the current page and use <a href="https://codex.wordpress.org/Function_Reference/wp_list_pages" rel="nofollow ugc">wp_list_pages</a>. So I did some research and decided to extend the functionality of my favourite plugin, <a href="https://wordpress.org/extend/plugins/advanced-custom-fields/" rel="ugc">Advanced Custom Fields</a>. Now when I create a new Page or Custom Post, I just select the menu from a drop down menu!
Feel free to try this add-on on your dev site, ask questions on the support link above, and please review this add-on. By leaving a rating and review, you help this plugin become even better!
<h4>Advanced Custom Fields Compatibility</h4>
This add-on will work with:
<ul>
<li>version 5</li>
<li>version 4</li>
</ul>

Advanced Custom Fields: Nav Menu Field

Does what it says

This plugin might be old, but it still works perfectly and does exactly what I needed. No PHP errors, warnings, or notices, either. Running with ACF PRO 5.6.7 and WordPress 4.9.1.

Oldie but Goodie

Let's don't make any mistakes here - this addon is perfect and needs no changes, that's why there is nothing to update here.

Used it in many sites. Thank you!

Let's don't make any mistakes here...

Add-On plugin for Advanced Custom Fields (ACF) that adds a 'Nav Menu' Field type.

Custom field finder vs Advanced Custom Fields: Nav Menu Field