To increase or decrease the level of detail shown in a report, in Reports (top row)>Edit (top right), select the row to be adjusted and use the expansion dropdown menu (circled below) to select the default level of detail in the report: collapsed, showing Groups, showing Groups and Subgroups, or fully expanded to show Accounts.
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Note: you can also select individual accounts, subgroups, or groups as rows. Each group and subgroup offers the option to expand.