How to insert visual compser post grid shortcode in a custom page template? [closed]

If that’s what they says in their docs then I think the time you’d spend trying to get around it will be much more than simply doing the following:

Create a page.

Put the grid shortcode in (normally, in the page builder).

Then save the page and visit it (as in go to the page on the website front end).

View source and copy the html produced by the shortcode.

Paste it in to your template, keeping all CSS classes/ids.

This will produce the exact same visual features, as long as all required vc stylesheets and js is being included. If not, then enqueue the required assests manually for that particular template.