To copy a Topic, click on the copy icon below. You can copy Subjects, Topics and Steps.
The new version will include 'Copy' after the title.
If you want to copy and move a Topic, select copy and then the arrow next to the new version.
You will then receive a pop up asking you where to move this Topic. Select the appropriate Subject from the dropdown and you're all set!
You can copy Subjects in both outline view and card view.