Currently, when importing from Excel, there is no way to prevent duplicates or to update existing items on a board. It would be ideal if upon Excel import you could select an option to update existing item column values if the item name matches.
We use a board to track collaboration with external parties around a sales pipeline and need to regularly update the status of the items from our sales system on a regular basis, but would like to keep the updates from the collaboration. Currently, there is no way to do this (outside of using the API).