Add additional global filter to Yearly Budget Sheet in Foundations Template

How do I add a filter to the Yearly Budget Sheet inside the Foundation template?

The functionality I am looking for is similar to what you can do within a pivot table.

For example, in order to aid my cash flow analysis, I would like to filter out one time events such as Bonuses (Income) and Home Improvement Projects (Expenses).

With that type of filter, I could easily toggle back and forth between my comprehensive cash flow incl. all income and expenses and my monthly cash flow from recurring activities.

How would I add that without breaking the functionality in the Budget Sheet. I want to use everything else as is.