How to move a user's reply into a new topic?

I once asked a question under someone else’s thread and it was modified by an administrator to a new thread.
Now I want to do the same in my forum. Take someone else’s reply that is not relevant to the original topic and re-edit it to a new topic.
But I clicked every button in the reply. None of them found the right way. Is there a permission setting that needs to be turned on somewhere first?

If you click the admin wrench in top right corner of the topic, you can then select the reply and move it to a new topic and category.