If using Kadence Elements to override a template, the WordPress Block Editor's "Preview in new tab 🔗" link renders the saved version of the post, rather than the unsaved changes in the block editor that the user is trying to preview. This code will fix that, but only fix it for the post content -- if there are other unsaved changes such as postm…

kadence-elements-preview-fix.php

<?php
/**
 * Kadence Elements Preview Fix
 *
 * This plugin fixes the content for Kadence Elements previews in
 * Gutenberg. When previewing, the unsaved content is spliced into
 * $GLOBALS['post'], but Kadence runs pulling the saved content
 * instead. This plugin ensures that the correct content is
 * displayed in the preview.
 */

namespace BigOrangeLab\Kadence\Elements\PreviewFix;

add_filter( 'the_content', __NAMESPACE__ . '\\preview_fix' );

/**
 * Fixes the content for Kadence Elements previews.
 *
 * When previewing in Gutenberg, the unsaved content is spliced into $GLOBALS['post'],
 * but Kadence (incorrectly) runs pulling the saved content instead.
 *
 * @param string $content The original content.
 * @return string The modified content for preview.
 */
function preview_fix( $content ) {
	static $guard = false;
	if ( is_preview() && doing_action( 'ktp_the_content' ) && ! $guard ) {
		$guard = true;
		$content = apply_filters( 'the_content', get_the_content( '', false, $GLOBALS['post'] ) );
		$guard = false;
	}
	return $content;
}