After every heist, statistics are saved to a CSV file. The file can be found at mods/saves/heist_statistics.csv. You can then import the CSV file into your favorite program (Excel, Google Sheets...) to look at beautiful data :)

The following statistics are currently saved in this order:
Heist name, difficulty, completion date and time, duration (sec), total XP, base XP, stealth bonus, player names, player perk decks