The following steps show how to add the Show Desktop icon to the launcher using Ubuntu 16.04.
- Click on the Ubuntu icon in the launcher
- Type ‘System Settings’ and click on the icon when it appears in the results
- Click on the ‘Appearance’ icon
- Click on the ‘Behaviour’ tab at the top of the window
- Tick the ‘Add show desktop icon to the launcher’ option
- Close the Window to save the changes.