Hi there, @RR36452.

It's my pleasure to help you add an account line to your existing budget in QuickBooks Desktop (QBDT).

If you're referring to adding an account line to your existing budget, you may create a new account in the Chart of Accounts if the account wasn't added yet.

1. Go to Lists.
2. Select Chart of Accounts.
3. Click New.

To add the account line, you may edit the budget created.

1. Go to Company.
2. Select Planning and Budgeting.
3. Click on Set up Budgets.
4. Select the budget created.
5. The new account created was now added under the Account column.

To know more about creating budgets in QBDT, you can check this article: Create a budget or forecast in QuickBooks Desktop.

Keep me posted if you have any other questions about budgets, I'll be right here to help you. Have a good one!