virtualLast/CustomContent.php

## cms_page_form.xml
<?xml version="1.0" encoding="UTF-8"?>
<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
    <fieldset name="content">
        <field name="custom_content">
            <argument name="data" xsi:type="array">
                <item name="config" xsi:type="array">
                    <item name="label" xsi:type="string"/>
                    <item name="formElement" xsi:type="string">wysiwyg</item>
                    <item name="source" xsi:type="string">page</item>
                    <item name="wysiwyg" xsi:type="boolean">true</item>
                    <item name="dataScope" xsi:type="string">custom_content</item>
                    <item name="additionalClasses" xsi:type="string">admin__field-wide</item>
                </item>
            </argument>
        </field>
    </fieldset>
</form>

## cms_page_view.xml
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
    <body>
        <referenceContainer name="content">
            <block class="MageVision\Blog15\Block\CustomContent" name="cms.page.custom.content" after="cms_page" />
        </referenceContainer>
    </body>
</page>

## CustomContent.php
<?php
namespace MageVision\Blog15\Block;

class CustomContent extends \Magento\Cms\Block\Page
{
    /**
     * Prepare HTML content
     *
     * @return string
     */
    protected function _toHtml()
    {
        $html = $this->_filterProvider->getPageFilter()->filter($this->getPage()->getCustomContent());
        return $html;
    }
}

## InstallSchema.php
<?php
namespace MageVision\Blog15\Setup;

use Magento\Framework\Setup\InstallSchemaInterface;
use Magento\Framework\Setup\ModuleContextInterface;
use Magento\Framework\Setup\SchemaSetupInterface;

class InstallSchema implements InstallSchemaInterface
{
    /**
     * Add Secondary Custom Content
     */
    public function install(SchemaSetupInterface $setup, ModuleContextInterface $context)
    {
        $installer = $setup;

        $installer->startSetup();

        $setup->getConnection()->addColumn(
            $setup->getTable('cms_page'),
            'custom_content',
            [
                'type' => \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
                'length' => '2M',
                'nullable' => true,
                'comment' => 'Page Custom Content'
            ]
        );

        $installer->endSetup();
    }
}
	<?xml version="1.0" encoding="UTF-8"?>
	<form xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_configuration.xsd">
	<fieldset name="content">
	<field name="custom_content">
	<argument name="data" xsi:type="array">
	<item name="config" xsi:type="array">
	<item name="label" xsi:type="string"/>
	<item name="formElement" xsi:type="string">wysiwyg</item>
	<item name="source" xsi:type="string">page</item>
	<item name="wysiwyg" xsi:type="boolean">true</item>
	<item name="dataScope" xsi:type="string">custom_content</item>
	<item name="additionalClasses" xsi:type="string">admin__field-wide</item>
	</item>
	</argument>
	</field>
	</fieldset>
	</form>
	<?xml version="1.0"?>
	<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
	<body>
	<referenceContainer name="content">
	<block class="MageVision\Blog15\Block\CustomContent" name="cms.page.custom.content" after="cms_page" />
	</referenceContainer>
	</body>
	</page>
	<?php
	namespace MageVision\Blog15\Block;

	class CustomContent extends \Magento\Cms\Block\Page
	{
	/**
	* Prepare HTML content
	*
	* @return string
	*/
	protected function _toHtml()
	{
	$html = $this->_filterProvider->getPageFilter()->filter($this->getPage()->getCustomContent());
	return $html;
	}
	}
	<?php
	namespace MageVision\Blog15\Setup;

	use Magento\Framework\Setup\InstallSchemaInterface;
	use Magento\Framework\Setup\ModuleContextInterface;
	use Magento\Framework\Setup\SchemaSetupInterface;

	class InstallSchema implements InstallSchemaInterface
	{
	/**
	* Add Secondary Custom Content
	*/
	public function install(SchemaSetupInterface $setup, ModuleContextInterface $context)
	{
	$installer = $setup;

	$installer->startSetup();

	$setup->getConnection()->addColumn(
	$setup->getTable('cms_page'),
	'custom_content',
	[
	'type' => \Magento\Framework\DB\Ddl\Table::TYPE_TEXT,
	'length' => '2M',
	'nullable' => true,
	'comment' => 'Page Custom Content'
	]
	);

	$installer->endSetup();
	}
	}