I want to be able to lower all windows and show the desktop from the command line, not
There is a useful command line application called
Thus - to mimic Control+Alt+D (or Super+D, or whatever the combination is you need), you can use one of the following commands:
I'm not sure fossfreedom's answer truly satisfies the requirement to "not use Ctrl+Alt+D"
Thus I recommend to show desktop the command:
To turn it off use