Group costs into a small number of meaningful categories rather than listing the entire income statement. Fixed versus variable, direct versus indirect, or value-chain stages can all work depending on the case.

Then prioritize based on size, recent change, controllability, and strategic importance. You can drill into individual cost lines only after the data points you there.

The opening structure should organize the investigation, not reproduce every possible expense. If useful, this guide on case structure vs. case framework gives more detail.