I selected an element and pressed CTRL + D to define som actions.
Afterward I clicked OK, but then I wondered why the usual flag wasn't shown... It took me quite some time to figure out that I had selected a group and not a single element, and when I pressed CTRL + D it actually opened the Behavior dialog for the page because you cannot add behaviour to a group.
Instead of automatically selecting the page Behaviour dialog, I'd like the system to give me an error message if I select a group and press CTRL + D:
"You cannot define behavior for a group."