LibreOffice 7.5 Help
Creates a new slide from every top-level outline point (text one level below the title text in the outline hierarchy) in the selected slide. The outline text becomes the title of the new slide. Outline points below the top level on the original slide are moved up one level on the new slide.
You can only use the Expand Slide command if your slide layout contains a title object and an outline object.
If you want to keep the original slide, choose Edit - Undo.