When selecting and deleting an item in the Timeline or Workbench, following rules apply:
Deleting an Item in the past: Anything (Playlists, Videos, Audio, Graphics, Events) that lies completely in the past cannot be deleted.
Deleting an Item in the present (= On Air): Playlists, Audio and Graphics that are currently On Air may be deleted. A warning will be shown.
Videos which are On Air cannot be deleted but skipped by clicking the Play Next
button in the Control Area.
Deleting an Item in the future: Anything (Playlists, Videos, Audio, Graphics, Events) that lies in the future may be deleted without warning.
If no warning is shown when deleting present items you can enable all warning dialogs again in the just:control Preferences.
Click the Reset Warning Alerts button as shown above.