A simple python3 script I wrote to hide or show your desktop. I only tested this script on ElementaryOS 0.4 Loki. You can use this script as a Custom Command for Hot Corners if you like.
If you like to, you can remove the ".py" extension of the file, make it executable with chmod +x /path/to/show-desktop and move it to /usr/bin. In this case you can just call show-desktop from the command line or the Hot Corners feature in order to execute the script.