I tried my best to do this. I found the location it is stored (.config/kcminputrc), I need the LeftHanded=true switched to LeftHanded=false. sed works but I can’t reload this setting. Restarting plasma shell won’t do it. I don’t want to relog either. kreadconfig5 --file ~/.config/kcminputrc --key LeftHanded also doesn’t return anything so I am not in the best position to use kwriteconfig5. I also don’t want to pull in qdbus and related dependencies unless absolutely necessary. Please help 
how good are you are writing javascript or qml code?
Well, I can code alright, but that route seems more complicated and would involve more dependencies. So far I am doing kcmshell6 kcm_mouse and click what’s need clicking. If I get too frustrated with this I’ll try the qdbus route. But I bet there’s a way to it without this or yolo scripting.