That's the core question. This is 99% of the value that any such tool provides. An open source project that had import flows for all the major banks & brokers

That's the core question. This is 99% of the value that any such tool provides. An open source project that had import flows for all the major banks & brokers into a well-defined unified format? Tremendous impact. A graphing tool that only imports a standardized CSV? I can do that in my spreadsheet in minutes.