My idea, instead of nesting the parent asset listing from the default type format bodycopy, was to nest it from the group (by parent) format bodycopy, passing the parent URL as a GET variable. However, this means that the parent asset listing's replacement root mode no longer works, presumably because the session variable %list_current_asset_id% is only set once in the type format bodycopy, not the group format. Bang goes another good idea.