You can turn the Wall Reference Lines on and off by going to View>On-Screen View Options and clicking Wall & Beam Reference Lines.
To set the Alignment of Stairs (Left, Right or Centre), use the Preview and Positioning Panel to pick on the appropriate hotspot:
When you place a Polystair and want to set the reference line, you can do this in the Preview and Position Panel… If you imagine facing the start of the stair you can choose the left, centre or right edge as the reference line.
When drawing a Wall you very often have to flip the Reference Line – rather than use a button on the Info Box, you can simply press ‘P’..
If you are about to create a new Polystair with Cadimage Stairs and would like to set the Reference Line position – go to the 2D Plan Preview and click the Left, Centre or Right Node point as highlighted below…
When placing walls make sure that reference lines touch, this will make ArchiCAD clean up the intersection.