Hello there, @Aisleofdogs.
When creating a budget in QuickBooks Online (QBO), you can compare it against your actual sales and expenses. Thus, adding a category row such as a fixed asset is not an option.
To know more about how the Budget feature works, here's an article that you can visit: Create and import budgets into QuickBooks Online. It also contains information on how you can edit, copy, or delete budgets.
Furthermore, you can also check out this article to learn more about running a report in QBO.
Please feel free to post a question in the comments below if you have anything else in mind. I'll be sure to get back to you. Have a great day!