register cmb2 metabox after title on admin page edit screen

register_cmb2_metabox_after_title.php

<?php

add_action( 'cmb2_init', 'source_banner_metabox' );

function source_banner_metabox() {

	$prefix = '_source_demo_';

	$cmb_demo = new_cmb2_box( array(
		'id'            => $prefix . 'metabox',
		'title'         => __( 'Test Metabox', 'cmb2' ), // Kept this as I don't want to remove the metabox wrap
		'object_types'  => array( 'page' ), 
		'show_names'    => true, 
	) );

	$cmb_demo->add_field( array(
		'name'       => __( 'Test Text', 'cmb2' ),
		'desc'       => __( 'field description (optional)', 'cmb2' ),
		'id'         => $prefix . 'text',
		'type'       => 'text',
	) );
}


function source_output_custom_mb_location() {
	cmb2_get_metabox( '_source_demo_metabox' )->show_form();
}
add_action( 'edit_form_after_title', 'source_output_custom_mb_location' );