The single_export feature allows the users to download a XML export file with only a single entry. A new option will be added in the 'Publish' metabox when you're editing a single entry.

You can either simply set it to true or pass it an array with the label to display.

Example:

return [
	'active'   => true,
	'type'     => 'cpt',
	'name'     => 'igmap',
	'supports' => [
		'title',
	],
	'features' => [
		'single_export' => [
			'label' => __( 'Download Map Export File', 'interactive-geo-maps' ),
		],
	],
];