I'm following along a tutorial [www.sidefx.com] for crowds. At 14:10 in the video, I try to populate my scene as well, however my parameters for layout and area size are greyed out.



Is this a limit of Houdini Apprentice or a bug?

Cut the connection to the second input. Layout options are available only when there is no second connection. Your ObjectMerge points are providing the layout.