If you want to free up some space on your device, you can remove downloaded showcases in the Showcase Workshop app.
To do this, find the showcase you want to remove and tap the small grey circle with a line in it directly below it.
You'll get a pop-up asking if you'd like to remove this showcase, so don't worry about accidentally removing one!
Once you remove a showcase the grey icon will change to a green cloud. This means that you can re-download it at any time by clicking the cloud icon!
Note: Removing a showcase does not delete the actual showcase from your device — rather, it removes it from your list of downloaded showcases so you won't be able to view it offline unless you download it again. It's a handy feature to free up space on your device.