When the number of slides becomes unmanageable, you can group them. By expanding and collapsing groups, you can view subsets of the slides instead of all slides at once. Groups also provide a useful overview for the project, and they provide a convenient way of deleting or hiding multiple slides at once (for example, slides that you don’t want to publish).
To help associate slides with their group, you can mark grouped slides with the same border color. The color is not displayed when the project is run.
The selected slides are grouped into a single group slide with their numbers and descriptions displayed on it.
Right-click (Windows) or Control-click (Mac OS) the group slide and select Group > Expand or Group > Collapse.
A faster way is to click the arrow icon on top of the group slide.