Mixing change at Propeller/Motor/ESC failure

I’m beginner to PX4…So I’m having trouble trying to do the following.
Please someone help me!

■What I want to do!
During flight → Flight unit (propeller or motor or ESC) failure → Detection → Mixing change

■What I want to know!
How to change to optimal mixing when the flight unit breaks down.
※flight unit = propeller/motor/esc
(Example : case of Octcopter,
①transition to mixing A when 1/8 flight unit fail
② transferred to Mixing B when 2/8 flight unit fail ・・・)