Balance Item: Accounts Section

Specify what accounts are to be displayed under this balance item in the financial statements that will be prepared according to the balance type to which this balance item belongs.  
To do that
1. Click the + Add new button above a table listing accounts that are to be grouped in under this balance item. 
Note: For a newly created balance item, the table is empty. However, for the pre-defined balance items, the table contains accounts that by default match this balance item.
2. Select an account from the list of accounts that are not attributed to other balance items of this balance type.
You can add multiple accounts, if necessary. They are added to the table as line items.
You can delete the accounts added later on.
You can change the selection of accounts even for the pre-defined balance items. You can delete the specified accounts and add new ones.
Note: The article describes one of the ways how to specify the location of accounts in the standardized structure of your financial statements. You can also define balance items under which accounts are to be classified/located/displayed while creating or updating accounts.
For more details, see Account Details: Balance Items.
There is an interrelation between the two options, as the selection always affects both balance item details and account details. For example, if you match a balance item to an account while creating or updating the latter, this account will be automatically displayed in the Accounts section of the balance item among other attributed accounts. The rule also works the other way round.
Following the logic described above, any changes made to the selection are reflected in both balance item details and account details.
More information
Set Up a New Account