Role Capability to use it

Hi,

in my case only one Role should be able to duplicate posts (custom post type in my case).

I didn’t see any capability check in your code. Maybe I just didn’t found it. As an solution I just remove it from the row actions:

add_filter( 'post_row_actions', array($this,'remove_row_actions'), 10, 1 );
public function remove_row_actions( $actions)
    {
        //The Post Duplicator Plugin doesn't check for an capability himself
        //So we have to remove it from the action row at a post
        //In our case only the Admin can duplicate posts
        if( get_post_type() === 'sa_classbook_course' && !current_user_can('administrator'))
            unset( $actions['duplicate_post'] );
        return $actions;
    }

Maybe you could just create a new capability and check for it ?

I Posted my solution for someone else who got this problem too.