The option to permanently delete the accounts in the Chart of Accounts (COA) is unavailable in QuickBooks Online (QBO).
Right now, the only way we can eliminate unusable accounts is to make them inactive in your account list. This is designed to keep your previous transactions under this account accessible for reporting purposes. Making this inactive helps lessen the usage and gives space to new accounts in your company file.
Furthermore, get equipped by learning more about COA. It enables you to use the correct accounts to track your financial information and provide better insights into your business.
Keep me posted if you have more questions about deleting an account. The Community always has your back. Have a good one!