Saving a Real File From Flutter Web, Instead of Downloading Another Copy

Build an editor on Flutter Web. The user opens budget.csv, edits it, hits save. They get budget.csv in their Downloads folder. They edit again, save again: budget (1).csv. Again: budget (2).csv. Their real file — the one on their Desktop that they opened — has never been touched. By the end of an afternoon they have nine numbered copies and no...