Pivot/Unpivot is one of those concepts that seems simple until you actually need it in production. I use the same pattern constantly when reshaping OHLCV crypto data — price feeds come in as wide tables (one column per asset) but most time-series analysis needs long format. Power Query's Unpivot makes that a one-click transform. Good luck with the PL-300 — the DAX filter context questions are the real trap on that exam.