Final deletion
You can delete definitely a selected object from the program by pressing the Del key or by using the Delete option from the Edit menu.
Graphical deletion
You can also delete the selected object from the graph, but not from the program, by pressing the Del key or by using the Delete the graphic option from the Edit menu.
The object is then "removed" from the graph but is still available in the list from the Place (entities, subtype entities or relationships) option from the Edit menu.
If you remove or delete an object, you will also remove or delete all the links attached to the object.
If an object that has been removed is then replaced on the graph (by means of the corresponding Place option from the Edit menu), all its links will also be replaced on the graph automatically.
Note: If the graphic of a link is deleted, the link will be actually deleted. Regarding links, the remove operation (Delete the graphic) has the same effect as the Delete option.