Oh I think you just mean a scrollbar.
This was removed deliberately as there aren't many use cases for it and it somewhat lacks other useful functionality. What you describe certainly is a valid use case, but actually you don't need to publish them first.
You just click through to the thread itself and do the editing there. The benefit of this is that it won't bypass things like edit history and you will get the full post editor rather than doing it in a text box.
Once you've done your edit, you don't even need to go back to the approval queue, you can just use the "Approve" button at the top of the thread to approve it (this also removes it from the approval queue).
With this in mind, I don't think we're going to backtrack on this now.