I think this works, though it's not quite the same as NX9. If I turn on horizontal and vertical alignment, I can get this snapping behaviour. The difference is that it adds a constraint (NX9 doesn't have this type of constraint). When I then draw another line across, that new horizontal...
When I'm using NX11, I miss a behaviour I get on another machine running NX9, where sketcher snaps lines to nearby perpendicular lines. Anyone know what setting achieves this?