Keyboard to Axis?

[GeneralFlaw]

Is it possible to convert two keyboard buttons to an incremental throttle lever?

[Etogerman]

Yes. You can use a shared macro variable and emit an absolute gamepad-axis event. Set the target of both mappings to gamepad.

Increase by one step:

add(throttle,4096).if_eq($throttle,36864,set(throttle,32768)).event(EV_ABS,ABS_Z,$throttle)

Decrease by one step:

add(throttle,-4096).if_eq($throttle,-36864,set(throttle,-32768)).event(EV_ABS,ABS_Z,$throttle)

Optional reset/idle key:

set(throttle,-32768).event(EV_ABS,ABS_Z,$throttle)

4096 controls the step size. Replace ABS_Z if the application expects another axis. The variable initially starts at 0, so use the reset mapping once if your throttle should start at -32768.

If you meant continuously increasing/decreasing while a key is held, the same approach can be wrapped in hold(...).