The rpress_email_templates filter allows you to register new email template names that can be applied to emails sent through RestroPress.
A new template can be registered by adding an additional key, value pair to the array:
function pw_rpress_register_email_template( $templates ) {
$templates['default'] = 'My Custom Template Name';
return $templates;
}
add_filter( 'rpress_email_templates', 'pw_rpress_register_email_template' );
Place your custom templates in a folder called rpress_templates/emails inside your currently active theme.