how to use the Google Tag Manager plugin for gatsb

Please note that I'm still learning to use Gatsby & React.

I have been trying to figure out how to properly use the Google Tag Manager Plugin for Gatsbyjs to insert tracking codes into my app.

The official documentation of the plugin does not provide a lot of insights and examples, so I'm not sure if I understand it completely.

What I want to do is to insert two GTM tracking codes into my app, one in <head> and one in <body>. With the static site approach, I could just copy and paste the GTM tracking codes into my HTML documents, however, with Gatsby & React, it does not work that way.

For example, I want to insert the following code to the <head>

<!-- Google Tag Manager -->
<script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
})(window,document,'script','dataLayer','GTM-XXXX');</script>
<!-- End Google Tag Manager -->

I open the gatsby-config.js file and paste the following under plugins

// In your gatsby-config.js
plugins: [
  {
    resolve: `gatsby-plugin-google-tagmanager`,
    options: {
      id: "YOUR_GOOGLE_TAGMANAGER_ID",

      // Include GTM in development.
      // Defaults to false meaning GTM will only be loaded in production.
      includeInDevelopment: false,

      // Specify optional GTM environment details.
      gtmAuth: "YOUR_GOOGLE_TAGMANAGER_ENVIROMENT_AUTH_STRING",
      gtmPreview: "YOUR_GOOGLE_TAGMANAGER_ENVIROMENT_PREVIEW_NAME",
    },
  },
]

It seems like the only thing I need to do here is replacing 'YOUR_GOOGLE_TAGMANAGER_ID' with my own GTM-ID. However, after I've done that and check the source code after the build, it shows

<script async="" src="https://www.googletagmanager.com/gtm.js?id=GTM-XXXXX;gtm_auth=YOUR_GOOGLE_TAGMANAGER_ENVIROMENT_AUTH_STRING&amp;gtm_preview=YOUR_GOOGLE_TAGMANAGER_ENVIROMENT_PREVIEW_NAME&amp;gtm_cookies_win=x"></script>

am I missing something here, Please help

If you're going to be using the plugin mentioned in your question then you can just insert that plugin in gatsby-config.js file inside plugin property.

However, if you just want to plop the <script> tag that GTM provides you then you'd have to customize the html.js file of gatsby a little. Basically, it will let you put anything you'd like just like in any of your other html files.