Hi Julian,
Thank you for reaching out.
I think you can create a settings page and set the max clone there. Before register, the meta box and custom fields for the post, get the max clone number and assign it to the field.
In this way, you do not need to remember the post ID to get the field value. For example:
add_filter( 'rwmb_meta_boxes', function( $meta_boxes ) {
$settings = get_option('option_name');
$max_clone = $settings['max_clone_id'];
$meta_boxes[] = [
'title' => 'Test Meta Box',
'fields' => [
[
'type' => 'text',
'id' => 'name',
'name' => 'Name',
'clone' => true,
'max_clone' => $max_clone,
],
],
];
return $meta_boxes;
} );