Enter the Tag Manager code on the Check-out page

Hello,

I would like to insert the code of the tag manager present on my site in the Checkout page (using the setting present in the Checkout page under setting).

To do that I insert the code in the "Order status page - Add tracking scripts and other customizations ". but after I done this, I haven’t seen any changes on the code of the page(that not show the tracking code).

Following this I was wondering if page customizations (including the insertion of the tracking code) was only possible through the shopify plus subscription?

Thank you very much for your answer

Best regards