Switching between custom templates in a post type of the admin menu

When at least one template exists for a post type, the ‘Post Attributes’ meta box will be displayed in the back end, without the need to add post type support for 'page-attributes'. The title ‘Post Attributes’ can be customized per post type using the 'attributes' label when registering a post type.

Templates for custom post types have been introduced in WordPress 4.7 and you can define one like this:

<?php
/*
Template Name: Full-width layout
Template Post Type: post, page, product
*/

// … your code here

I recommend you to check my official post about it to learn more.