3.8 Deleting Subjects

    The edit command Delete (called from the Edit menu, or by the accelerator <Ctrl+D>), removes all subjects from the selection. If a node is deleted then all its adjacent edges are deleted too. If a node has duplicate shapes (see section 3.10) of which some but not all are selected then a question dialog is raised asking whether you want to delete all duplicates (and henceforth the node in the graph) or that you only want to delete the selected duplicate shapes.

The Edit menu command Delete All removes all subjects, selected or not. Before the command is executed, you are first asked by means of a question dialog if you really want to delete your masterpiece. 

Fortunately, like all commands, deletion commands can be undone with Undo.