Como Mapear eventos no GTM via dataLayer?

Topic summary

A user needs to track the start of checkout for leads using Google Tag Manager (GTM) via dataLayer. They have the necessary code snippet that pushes a ‘start_checkout’ event along with page category, title, and URL to the dataLayer:

window.dataLayer.push({
  event: 'start_checkout',
  pageCategory: 'categoria-exemplo',
  pageTitle: document.title,
  pageUrl: window.location.href
});

The main question is: which Liquid template file should this code be added to in order to fire at the beginning of the checkout process.

This appears to be an unanswered technical question with no responses yet.

Summarized with AI on October 29. AI used: claude-sonnet-4-5-20250929.

Preciso traquear o inicio de checkout de leads. Normalmente utilizo o trecho do código abaixo:

Mas não sei exatamente em que arquivo liquid deve adicionar por exemplo no inicio de checkout.