Can keys EXT/ENT/LRUD be used to start/stop timer?

It seems not supported, please tell me if I am wrong. However using these keys should be better so that switches can be used for other functions.

No, these key are dedicated as command keys in the software.

On the hardware side there is no difference compared to the other keys and in theory it can work. The difficulty would be to decide on consistent rules for such dual function keys - when a press is meant as command and when as function key.

I think that you can always use the R(ight) button to reset the timers (but not the permanent).
If you configure a timer with a Start cmd set to None, it will start/stop with the L(eft) button.

Seems your suggestions is not working in my Devo 8S

May I ask? Somehow I was successful at making a timer start with the throttle, once the throttle is raise, collective is given. But how do you make a button to reset the timer?
I hope you might help me, please?

On Devo6/8/12 short click on a timer start/stop it, long click reset it.
On Devo7/10 R(ight) button start/stop timers with switch set to None, L(eft) button reset all (not permanents) timers.

I have tried Devo 8S with Deviation, but I cannot find any of the ENT/EXT/UP/DOWN/LEFT/RIGHT buttons have any effect to the timers.