Stacking places siblings on top of one another to reduce horizontal space. This is useful for siblings about whom little is known or who are less central to the chart.
To stack a sibling: select them in editing mode, right-click (or click the … button), and choose "Start sibling stack". Then select the next sibling and choose "Continue sibling stack". Repeat for as many siblings as needed.
You can have more than one stack in a family. To start a second group, use "Start sibling stack" on another sibling.
To unstack a sibling, right-click and choose "Don’t stack sibling".