Add custom form elements in product add/edit form in specific group section in Magento 2

Here we’ll learn how to add custom form elements in product add/edit form in specific group section in Magento 2

Using magento2 ‘adminhtml_catalog_product_edit_prepare_form’  observer we can add custom form elements in product add/edit form.

1# First we’ll define observer (event) in event.xml file at folder app/code/NameSpace/ModuleName/etc/adminhtml

<?xml version="1.0"?>
<!--
/**
 * Webkul Admin events
 *
 * @category    Webkul
 * @author      Webkul Software Private Limited
 *
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="adminhtml_catalog_product_edit_prepare_form">
        <observer name="custom_product_fields" instance="NameSpace\ModuleName\Observer\CatalogProductEditPrepareForm" />
        <!-- CatalogProductEditPrepareForm is name of class in which we'll add custom fields in form-->
    </event>
</config>

2# Now create CatalogProductEditPrepareForm.php class file in app/code/NameSpace/ModuleName/Observer

<?php
/**
 * @category    Webkul
 * @author      Webkul Software Pvt. Ltd.
 */
namespace NameSpace\ModuleName\Observer;

use Magento\Framework\Event\ObserverInterface;

class CatalogProductEditPrepareForm implements ObserverInterface
{
	/**
     * @var \Magento\Framework\Registry
    */
    protected $_coreRegistry;

    /**
     * @param \Magento\Framework\Registry  $coreRegistry
     */
    public function __construct(
        \Magento\Framework\Registry  $coreRegistry
    ) {
        $this->_coreRegistry = $coreRegistry;
    }

    /**
     * product from prepare event handler.
     * @param \Magento\Framework\Event\Observer $observer
     * @return $this
     */
    public function execute(\Magento\Framework\Event\Observer $observer)
    {  
        $form = $observer->getForm(); // $observer contain form object

        // get your group element in which you want to add custom filed
        $fieldset = $form->getElement('group-fields-id-in-which-you-want-to-add-elements'); 

        if ($fieldset) {

            // get current product if you want to use any data from product
            $product = $this->_coreRegistry->registry('product');
            $fieldset ->addField(
                'custom-field-1',
                'text',
                [
                    'name' => 'custom-field-1',
                    'label' => __('Custom Field 1'),
                    'id' => 'custom-field-1'
                ]
            );

            $fieldset ->addField(
                'custom-field-2',
                'text',
                [
                    'name' => 'custom-field-2',
                    'label' => __('Custom Field 2'),
                    'id' => 'custom-field-2'
                ]
            );

            // You can set any data in these elements for display default value
            $form->addValues(
                [
                    'custom-field-1' => 'data according to you', // ex. $product->getName()
                    'custom-field-2' => 'data according to you'
                ]
            );
        }
        return $this;
    }
}

Note:- its use for display data on form and you can get data on submit but Data will not save with product …