You can attach sub accounts to a specific account without using a custom group.
Select Financials > Global Ledger > Setup > Finance Enterprise Group > Maintenance.
Open the finance enterprise group and click the Accounts tab.
Open the account for which to add the sub accounts.
Click the Sub Accounts tab to view the existing sub accounts.
Select the sub account or sub accounts to attach to the account in a chart of account.
Select Actions > Create Chart Account
Specify this information:
Add To Charts Where Account Exists
To add the selected sub accounts, specify the account if it is already included in the chart. You can also specify a like account so that the sub accounts can be added to same chart branch.