I find the easiest way to see the wall outline of another storey is to copy/paste these to the required storey and explode them where they become 2D lines and fills.
You can then edit the lines, fills and layer to suit your needs.
Remember that if you change your reference walls below you will also have to change these copied walls manually or repeat the above process.
Nick
ArchiCAD 4.1–22, Mac OS 10.14.x iMac 27" 3,2Ghz Intel-Core i5