you need to create the topic in the Staff category then move it to that topic. you should be able to search and find the topic title you created when you get to that above screen. note that topics, which are akin to threads or discussions, are under the categories, which are like forums/sub-forums. you should have a restricted category called Staff (it’s a default category for admins and moderators only). create a topic(s) in that category to move your posts to. once there, only staff will be able to view the post.
i’m not really clear on why you don’t just use the flagging functions in the review panel.