Well I surely didn't mean to bust any bubbles. I'm "pretty good" with electronics. This one is a day at the beach.
Look's like others that pop out suggestions after having photos like you put up on assumption that since theirs is wired the way it is, yours should be too.
Good thing you asked here and you didn't blow the circuit in your controller.
Not being able to identify a limit switch, hall sensor, or reed sensor in this "hobby" these days will lead to a disaster.
But....there must be a provision to add some sort of sensor in your gearbox. A little rewiring of the limits and a couple of diodes, a magnet and sensor of your choosing could be done easily if you had a donor unit. Heck, I'd do it. I need a good heavy duty 36" actuator here.
Edit:
Your assy. should look like this The sensor is a hall effect in in a micro switch form housing with a trigger wheel.