@ClaytonM You were right!
The “Parallel” activity seems to be designed to invoke workflows, it doesn’t work if you put activities inside.
Example below. I created 3 workflows, each with a delay of 5, 10 and 15 seconds after which a message box popped up. When I ran this, all three messageboxes popped up one after the other with a 5 second interval, exactly as expected. This is very interesting stuff, will definitely look into it. As long as workflows don’t interfere with each other you can make a robot do multiple things at the same time.
@ UiPath, it would be nice if the Parallel activity is documented. 
