How to assign my 2-position switch on Taranis as an arming switch

Hello!
I’m assembling px rover now, and want to assign my 2-position switch on Taranis as an arming switch.
Taranis has two 2-position switches, which is configured on QGroundControl as RC channel 10 and 12.

At first, I configured channel 10 as an Arm switch channel. By doing so, I was expecting to arm/disarm my vehicle only with this switch(of course I always use the safety button first as a local arming), because the rover is controlled by throttle(forward) and rudder(yaw turning) and I think it would be dangerous to use arming gesture. I could arm with this channel 10 by turning up the switch, but could not disarm by releasing this switch.

I found the parameter RC_ARMSWITCH_TH, which set the threshold value to determine wether it should permit the arming. But I cannot find parameters relevant to disarm.

So, How can I arm/disarm the vehicle only with my 2-position switch? Currently, only arming is possible.
Thank you for reading my topic and please leave me a feedback if you can give me some advice.