Most UML tools offer some sort of facility for automatic layout of diagrams. The MagicDraw™ UML tool offers powerful heuristic layout algorithms. And don't be afraid, there is an UNDO function.

That said, Dr Darren usually prefers fine control over diagram layout using techniques such as «wrapper» Components. And one can even combine manual layout with automated layout of selected element symbols.

The main thing is to explore the possibilities.