Just out of curiousity MAV_CMD_GUIDED_CHANGE_ALTITUDE is in ardumega dialect but not executable?

Any idea where

MAV_CMD_GUIDED_CHANGE_ALTITUDE43001

is displayed in the Ardumega mavlink dialect but it is not executable.
I search thru ardupilot website there is nothing about this command.
Even in guided mode, it doesn’t show this command.

Isn’t this command part of Ardupilot?

Did you tested it on a real vehicle? What was the exact return code?

No I test it on SIM and it just stated command unsupported

And did you use the SITL compiled from github master branch? Or did you use an older version? which one exactly?

I follow the page instruction to install.

https://ardupilot.org/dev/docs/setting-up-sitl-on-linux.html

That should give you a fresh compiled SITL from Ardupilot’s master github branch.
If it is not implemented there, it is not implemented anywhere. Or did you checked if there is a github pull request adding this feature?