Hi @Romans323. I'm here to provide you information about adding line items to budgets.
This option is unavailable since accounts from budgets are coming from your chart of accounts. If you need more line items, you need to add more accounts.
You can uncheck the Hide empty rows to see all the items you added to your budget. Refer to the screenshot below:

If that is not the case, you can add an item to your budget by creating new accounts to your chart of accounts.
Here's how to create new accounts:
1. Go to Transactions.
2. Select Chart of accounts.
3. Click New and fill up the information needed. Hit Save.

After you create the necessary accounts, we need to create a new budget. Here are the steps:
1. Go to Settings then choose Budgeting.
2. Select Create budget.
3. Click the Budget type and Budget format.
4. Hit Next.
5. Review the details if it is good hit Save.
Moreover, You can monitor your financial objectives by running specific profit and loss budget reports.
Furthermore, you can visit this link for further information about creating and managing budget forecasts.
If you still have questions or concerns about editing budgets, click the Reply button. I'm always here to help.