I noticed this too.
It's unfortunate because there are times when I use Custom Edit to place my vegetation and there are times when I want to remain in custom edit but array a line of trees or shrubs at set intervals. The workaround was to duplicate the Forest object, set it to Generate distribution along a path, then in the original Forest object, attach the new items that have been arrayed along a path. Would it be possible to bring that functionality back in an update specifically for Custom Edit distribution?