With the KDE 6 mega release the shortcut “Ctrl_Esc” for launching the process monitor disappeared. It is intentional.
To get again a shortcut to launch “process monitor”, follow these steps.
launch “system settings”
select “keyboard”
select “shortcut”
sect “add a new” > “command or script”
Type"plasma-systemmonitor --page-name Processus — System Monitor"
click on “add a custom shortcut”
type “Alt_Esc”
click on “apply”