How to enable throttle hold in current devo8 build

Isn't that transmittion hold?

There is no dedicated throttle hold functionality in deviation as there is no dedicated throttle channel either.
I used to use the channel's safety feature for it, or alternatively you can use a plus complex mixer page too...

Complex mixer - example at last page of User's Manual (page 21), page 4 of complex mixer, for 'Throttle Hold' used 'GEAR' switch.

Channel configuration - (page 14), Safety: [switch], Value: -100%.

suvsuv wrote: Thanks FDR. So I need to figure out a way to control and monitor throttle channel if I want to provide direct setting for Thro Hold feature. Do you and PB has any suggestion about it

If you want to implement your own traditional interface, which should have a fixed throttle hold feature, you have to determine first from the protocol, which channel is the throttle.
Then the question is, do you wish to use the current mixer functions in the background, or will you reimplement the whole operation from stratch. In first case the aforementioned safety feature is your best bet...

However in that case you should support some multi engine scenarios as well, and implement your throttle hold to take it into account...
In deviation any channel can be throttle, you can cut them all if you wish...