I have a skin that allows me to open, monitor and close particular applications based on this thread: https://forum.rainmeter.net/viewtopic.php?f=5&t=4194. The skin works fine for all applications with one exception: the code to close calculator.exe does not respond. Here's the relevant code:
Seems that the new calculator requires the /F parameter to close it. Also, no need to fire up Powershell for this.
This is likely due to the fact that the calculator is now a "windows app" and all the old calc.exe and calculator.exe ways of calling it are really just "stubs" that load the new app. I suspect that RunTimeBroker is holding open the app when you try to close the "stub", and you have to force kill it to make them let go.