Customize the GET param used for auto populate WP Job Manager Field Editor fields

functions.php

<?php

add_filter( 'job_manager_field_editor_url_populate_from_key', 'smyles_auto_populate_from_get_custom', 10, 3 );

function smyles_auto_populate_from_get_custom( $meta_key, $args, $return_default ){

	if( $meta_key === 'job_title' ){
		return 'job_title_custom';
	}

	return $meta_key;
}