To simplify your script remove the handler to see if the whose clause will work with a list.
It doesn't.
tell
application "System Events"
setappNameList
to every application process
whose nameis in {"Keyboard Maestro", "Finder", "Script Debugger"}
end tell
To accomplish this you'll need to get the name of every application process then step through your list of targeted applications and find which ones are in both.