Grouping/ungrouping a set of objects should be available in the coming versions to help you move, resize and rotate a group of objects.
Meanwhile, here are two workarounds:
- you may select the objects you want to elevate and choose Furniture > Modify... menu item to change their elevation, but then, of course, all the selected objects will have the same elevation,
- you may select these objects, copy paste them in a new home, export that document to OBJ format with 3D view > Export to OBJ format... menu item, import the exported OBJ file with Furniture > Import furniture... menu item, and move the imported group of objects.