Hello again Tom,

You also don't want to do this thing where you break down a feature into parts like you do with https://www.openstreetmap.org/way/1396718878. You'll want to draw the rough as a single polygon and the two bunkers inside and then combine them by selecting all objects and right clicking one of them and selecting "Merge" (I think that's what iD calls it). This will create a proper "multipolygon" with the inner/outer features labelled correctly. Let me know if you have any question and I'll gladly help clarify things. thanks.
