The second way to configure a slide’s hierarchy is to click on the green arrow on the selected slide. This method will work if you selected only one slide.
If a button or an arrow is inactive, you can't change the nesting level in that direction.
The next nesting levels become available automatically: if the slide is located on the second level, the slide that follows it can be moved to the third level, and so on.
The maximum number of nesting levels is eight. Use the «-» and «+» icons to the left of the upper-level slide to expand and collapse the enclosed slides.