Here first my try in sh3d plugin form: http://www.mediafire.com/file/vlm3wjesgk38pjj/SH3DFurnGrouper.sh3p
Issues: Grouping work only in serach list mode. Sorry.
Known bugs:
1. After first initializing second frame not grouped. After first click in it - groups will appear.
2. After switching List->Tree->List selected furniture may be freezed. Only application restart solve it.
Sorry for this. If anyway your interest will keeped - i will work on it.