Choose the Delete tool and drag diagonally until a red highlight appears on the structure you want to erase. When you release the left mouse button, the highlighted parts will be deleted.
You can erase an atom or a bond by selecting the Delete tool and clicking on it.
Make a selection, then delete it by clicking on the Delete tool or pressing the Delete button on the keyboard.
In the case of deleting a bond, its atoms will not disappear from the canvas. On the other hand, if you erase an atom, its bonds will also be deleted.