How to check if WP saved via LUA script

Hello friends. I set up my RC and Pixhawk to save waypoint using switch via RCn_option. But sometimes the WP is not saved (may be due to some signal problems). and I don’t know it until I download mission to PC or smartphone. It would be easier if I get sound notification on my RC if the WP was successfully saved. I have the chip RC which is FlySky FS-I6 with 14channels firmware installed. There is no direct option to make sound when WP saved. However there is an option to alarm when the value of some sensors is lower or high than some value.
The idea is to track saving waypoint? and if waypoint was saved then for a second change the value of sensor I don’t use (for example temperature) and get it back to start value via script. Thus my RC makes sound alarm and I know that the WP was actually saved.
I hope I explained everything clear. Any ideas how to make it? Or maybe ideas how to make sounds on RC the other way. Thank you.

See here: Change sensor value via Lua script - ArduPilot Lua Scripting - ArduPilot Discourse