Yes, there's a a global preference for this, which you can enable when creating the report and then disable (if desired) the rest of the time.

To create a Trial Balance report showing only the sub-accounts, go to Edit | Preferences | Accounting | | Company Preferences and then in the Accounts box, enable "Show lowest subaccount only".

When selected, the report will display only the sub-accounts.

The preference also impacts how accounts display in registers and on transaction forms like checks (and mostly wherever accounts appear), making it easier to see the sub-account in use.