Expanding and collapsing tasks
Use the 'expand' or 'collapse' options to adjust the range of Jira issues visible in form of a Waterfall.
You can use the automatic options to adjust the whole view at once, or do that manually with each level of hierarchy by selecting the '+' or '-' button visible at the parent's row.
All your estimates can be rolled up to the parent level to generate a report. To learn more about configuring the aggregations go to the Columns view section.