I managed to get my desktop settings so that files on the desktop were sorted automatically. But I didn’t want that. I edited the ~/.kde/share/config/plasma-desktop-appletsrc file and set the sortingStrategy=0 and that disabled automatic alphabetical desktop sorting.
I wanted to run an application on my desktop when I dropped some files on it. To do that I created a process.desktop file like this:
#!/usr/bin/env xdg-open [Desktop Entry] Icon=unknown Name[en_US]=process Name=process Type=Application Exec=/home/jj5/bin/tmp/process-test %F