You need ti save it in the DS-format content folder, not the Poser-format runtimelibraryprops folder.  DS script files (.ds/.dsb/.dsa/.dse) are only visible in the Poser-format runtime if there is a Poser file of the same name, in which case the script is run instead of the Poser file.  DS-format scene files (.daz) aren't visible in the Poser--format runtime at all.

If you want a prop which loads from the runtimelibraryprops folder in both DS and Poser formats, there's a trick to it.  You make sure the .daz and .pp2 files have the same filename, and put those two files (and the .png file for the .pp2, you don't need a separate .png for the DS file) along with a .ds file with the same name containing the following:

// Load a scene file instead of a Poser file

if ( getArguments().length != 0 ) {
    var sourceName = getArguments()[ 0 ];
    var periodPos = sourceName.findRev( "." );
    if ( periodPos != -1) {
   sourceName = sourceName.left( periodPos ) + ".daz";
   App.getContentMgr().openNativeFile( sourceName , true );
    }
}
=====================================
When you click on the .pp2 in DS (in DS3 there'll be a scroll in the upper left corner of the icon to let you know there's a .ds file there), the .ds file is executed, which loads the .daz file.