Hello Chris,
When mapping a virtual switch bidirectionally via MIDI (either using auto-detect, or manually), Hauptwerk will always turn the MIDI switch on whenever the virtual switch is on, and vice-versa. For example, if you were using solenoid-actuated MIDI draw-knobs or tabs, then attempting to do the opposite would probably cause an infinite loop and oscillation (or maybe even a fire!).
If you want the MIDI switch's lamp/solenoid-draw-knob/tab to be *off* when some coupler is engaged internally (e.g. perhaps for something along the lines of a ventil) then you would need to add a second switch in your organ definition that was linked to the first with an inverting action, i.e. so that the user-controllable/mappable switch always had the opposite state to the internal coupler action node switch.