Idea is to embed a draw.io image in the pages content. For eg. you connect it to specific diagram, select a page within diagram, and then that specific draw.io diagram is embed in the gitbook page and is updated if any changes occur on the original file. Google docs already have this integration/plugin and it works really good :)
Google Tag Manager (GTM)
Google Search Console
To integrate a property with Search Console, you need to either verify with Google Analytics, a DNS provider, or by adding a meta tag or TXT record. Since Gitbook uses special Analytics stuff, I can't verify.