You can move objects to certain places outside the starting area.
Rods placed outside seem to disappear after starting the level.
I couldn't manage to drag connected objects.
But wheels and target objects are easy. They can even placed over
eachother, or directly in the goal.
See for example http://fantasticcontraption.com/?designId=195187
Here is how you do it. Place an object. Put it somewhere near the edge.
Now pick up the object but don't move it (just hold left mouse button).
Now press the right mouse button to bring up the flash menu.
Choose something like show all. (release left mouse button and click
the option). You should now be able to move the object while
you are not pressing any mouse button. Move the object just over
the edge so a red cross appears. Now press and hold the left mouse
button. The red cross disappears and you freed the object.