Please note that when you make a change to a DES in a project using a DES editor, the change is made immeditately to the project's DES data structure and is seen by the entire project. If you try to close the editor without saving the DES, the dialog below pops up.
Click on Cancel to return to the editor, Revert To File to discard unsaved changes and reload the DES from its file, Commit Later to keep the unsaved changes but not save changes to disk, and Commit to save the changes to disk.