Dummy Assets
1
Download the Dummy Assets: GitHub Link
Add them to UDKGame/Content and verify in the Content Browser:
2
Right click a map package and select Fully Load:
3
Drag an asset into the map, or Right click in the 3D editor and Add the object:
Immediately open Properties (F4) and put a useful name in the Tag field:
Save Current Level will update the Scene tab, then sort by Tag to find the invisible Dummy Assets: