Potlatch can already import waypoints from uploaded gpx file with attributes but it is a bit tricky. Gpx file need to have at least one valid track, otherwise it does not get uploaded, and then you need to accept waypoints one by one with Potlatch. I guess it is more simple with gpx than arbitraty CSV files because waypoint attributes are fixed. But getting coordinates and fields , and directly to JOSM from gpx file would be a very good help when transcribing recorded waypoints from GPS. Of cause I can already see waypoints as markers in JOSM and it is much better than nothing.