If you are editing a name of an element in the diagram editor you can press Escape to cancel editing without confirming the done changes.
The active tool in the toolbox is changed to Selection tool after pressing the Escape key.
If a nested element is selected in the diagram editor, its parent container is selected after pressing ESC.
If multiple elements are selected or a diagram element without container, the selection is cancelled on ESC.
Fullscreen mode can be closed using ESC key.
ESC key can be pressed when resizing an element to cancel it and to restore the element bounds before the resizing started.
Also any element inserting (including smart connector) can be stopped on ESC key press.