There is a [JOSM plugin PolygonCutOut][1] for splitting multipolygons. See also https://josm.openstreetmap.de/ticket/18295#comment:18
[1]: https://wiki.openstreetmap.org/wiki/PolygonCutOut
There is a [JOSM plugin PolygonCutOut][1] for splitting multipolygons. See https://josm.openstreetmap.de/ticket/18295#comment:18
[1]: https://wiki.openstreetmap.org/wiki/PolygonCutOut