<?php
namespace LearningCustomBlockAdminhtmlProduct;

use MagentoCatalogBlockAdminhtmlProductEdit;

class ProductEdit extends Edit
{

    /**
     * @var string
     */
    protected $_template = 'catalog/product/edit.phtml';


}

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">


<!--<preference for="MagentoCatalogBlockAdminhtmlProductEdit" type="VLCSolutionsDynamicsNAVBlockAdminhtmlProductProductEdit"/>-->

<type name="MagentoCatalogBlockAdminhtmlProductEdit">
    <plugin name="custom_product_edit" type="VLCSolutionsDynamicsNAVBlockAdminhtmlProductProductEdit" />
</type>

</config>

<h1> Hi I'm extending product edit page</h1>
....
//below is the product edit.phtml file coding here i'm not posting.