This plugin allows creating multipolygon by one click, which is easier than using traditional way using relation editor. Just select some ways and press the button. Polygon will automatically detect which of the ways is the outer way and assign roles automatically.
The plugin check the ways to be closed to avoid creating invalid multipolygon.
- Creates only one multipolygon at time - if you select ways that could form two separate multipolygons, results won't be what you expect.
- Does not know about "advanced multipolygons", where some ways may be consisting of more than one ways
- The check which way is outer may not work perfectly if some of the inner ways cross the outer way and protrude significantly from it.
(so in fact there are more outer ways and the multipolygon is "invalid")