Example: we have an Employee category, which is linked to a Team category. By default, we've worked out Salaries by Employee, and now we're interested in seeing Salaries by Team.
Click on the Category icon in the referenced variable in the formula, and then select the desired category and click Group By.
Sometimes you'll want to select a single item from a category and use it in a formula.
Click on the Category icon in the referenced variable in the formula, and then select the desired category and then click on the individual item you want to filter by.
Example: if I want to do a calculation only based off the Engineering Team's salaries, you would select engineering under Team.
Sometimes you'll also want to aggregate away a category, if you no longer care to see that level of granularity.
Example: If I've filtered Salary by Employee for just the Engineering Team, but I no longer care to see the Employee breakdown, I would aggregate the Employee category.