Similar to Windows “End Task” option in the taskbar. The current “Close” sends a close request but sometimes you need the app to be killed / closed forcefully, you can do that through the terminal with kill or pkill but sometimes it’s faster to do it via the context menu. I already implemented it in this discussion: QML: Changing the taskbar context menu close button, to kill the app? - #7 by reisub
But it’s a bit hacky
You can also go with ^Ctrl⇧ ShiftEsc to get a skull cursor which kills on contact 
Menacing, I never got that to work though
It was Meta + Ctrl + Esc for me, not Ctrl + Shift + Esc. It doesn’t really do what I want it to do though, you gotta click on the window to kill it but the window could be unavailable so “cursoreaper” doesn’t work in that case
Btw how did you add those keyboard visuals? Manually with <kbd>?
Compose<< opens <kbd>
Compose>> closes </kbd>
ComposeKN </kbd><kbd> for “key next”