I have yet to find a way to create a shortcut on the desktop. Like in Windows, in the Main Menu, that's possible. Here I can't, since I have no panel,
The only way I could figure, is to add a temporary panel, open an application, and then drag the application icon from the temporary panel on the desktop, and remove the temporary panel.
There must be a better way!!?
Something similar on how to get a widget onto the desktop .... .?!

Thanks in advance,

Uwe

This works for me in Plasma 5.8:

Open Krunner (alt-f2), search for the program and drag-and-drop the result that pops up below it