Override the current Configurator theme using a postmeta

override-configurator-theme.php

<?php

if ( ! defined( 'ABSPATH' ) ) die();

add_filter( 'mkl/pc/theme_id', function( $default ) {
	global $post;
	if ( ! is_a( $post, 'WP_Post' ) ) return $default;
	// Example 1: use the post meta to get the theme
	if ( get_post_meta( $post->ID, 'mkl_custom_page_theme', true ) ) return get_post_meta( $post->ID, 'mkl_custom_page_theme', true );

	// Example 2: Check the current post ID to decide which theme to use
	// if ( 349 === $post->ID ) return 'float';
	return $default;
} );