An trick I use for this kind of task (multiply furniture at different positions only on X or only on Y; e.g. steps of stairs).
1. Select the object and Ctrl+C
2. Ctrl+V and then Delete (first paste are placated on a different position than the original and I don't need it)
3. Ctrl+V again (the pasted object will be exactly superpose over the copy one and became selected)
4. Ctrl+Shift+E or right click and manually edit the position and/or elevation