To delete objects, you can activate the Eraser Tool:
When you drag the mouse cursor, this tool being active, the objects which would be deleted after clicking are highlighted in red.
To erase a bond or an atom, click on it when this tool is active. An atom is suppressed with all its bonds. While the button is pressed, the objects to delete appear coloured in red if the pointer remains near them and revert to black if the mouse pointer is moved away. When the left button is released, the objects coloured in red are deleted.
You can also delete whole molecules and groups of objects at once with the help of the Selection Tool.
Automatic objects cannot be deleted with this tool.
The eraser tool has an empty property page.