LibreOffice 24.2 Help
To select an object that is covered by other objects, hold down OptionAlt and click through the objects until you reach the underlying object. To cycle through the objects in reverse order, hold down OptionAlt+Shift when you click.
To select an object that is covered by another object using the keyboard, press Tab to cycle through the objects on the slide. To cycle through the objects in reverse order, press Shift+Tab.