Hi there,
Kindly add a child theme to Pro. After that kindly add the code below to functions.php file of your child theme:
function third_party_tracking_code() { ?>
//ADD the JSON code HERE
<?php
add_action( 'wp_head', 'third_party_tracking_code' );
The code above uses wp_head filter. Inside that block of code you can add the JSON tracking cod e that you have.
For more information about the customization of the theme and adding stuff to the header or different part of the website please kindly read the articles below:
https://theme.co/apex/forum/t/customizations-actions-and-filters-in-x/208
Thank you.