If you would like to exclude an Account from reporting or forecasting, the option to archive is available within the Chart of Accounts.
Head into your Organisation's Chart of Accounts, locate the Account in question and select it. You'll notice an option to archive will become available:
Once archived, the Account will be hidden from all reporting, providing that within the reporting period in question, the Account has no data. If it does have data, it will appear.
To view your Chart of Accounts including the archived Accounts, simply click the option 'Include Archived Accounts'. You can unarchive by selecting the Account in question and clicking 'Unarchive' option that will become available after the selection has been made: