To duplicate an expense:

1. Open the paid expense you want to copy. Duplicate is only available on paid expenses; an unpaid expense shows "Mark as Paid" instead
2. Click "Duplicate" in the header, or use it from the "Actions" card in the sidebar
3. A new unpaid copy is created with the same details, dated today
4. Adjust the amount or other details as needed

Tip: Useful for regular expenses that occur with slight variations each time.