Hi greg_allen,
Welcome to the QuickBooks Online community family! It's great you're using the Budgeting feature to easily track your budgets' sales and expenses. I'll be happy to share more on this.
At the moment, there's no option available to include a one time expense and divide it into a 12-month budget. I can see how this feature could have benefited your business, and I invite you to submit feedback directly to our engineers. Your comments are crucial in driving innovation to offer the best QuickBooks experience we can.
In the meantime, feel free to explore our Apps menu to find any third-party app that could better assist you with your task.
Don't hesitate to reach out if you need anything else.