Navigating the report table is done by clicking on a group header in the table. The group headers uses an expand and collapse functionality similar to an accordion menu. When you click on the group header you expand the contents of the group. If there is sub groups within that group they are displayed until you eventually drill down to the line items.
Grouping is useful to get a better overview of a lot of report data without needing to navigate through each day at a time.
Use the sidebar to set up to 3 levels of grouping within the report. Each group can be defined separately.
Please note: some report templates do not allow for certain types of grouping due to how results need to be calculated.