It would be nice if decorative item placement in the builder functioned more similarly to the item placer tool outside of the builder: outside of the builder you can place items on one another (with certain restrictions) but in the builder, anything that’s not a building piece is filtered out of the _location_filter (and then also checked against in the server build service add_fixture). Presumably some sort of “placement structure” reference would need to be added, perhaps doubly-linked so the builder could easily determine a proper placement order.
Of course these item placement bugs would probably also need to be addressed for this to function properly.