Lock Processes pane selection in place

[crabdancing]

Checklist

• I've looked through the documentation and existing open issues for this feature/feature request.

Describe the feature request

It feels awkward to kill processes with the process view, because, depending on how the processes are sorted (e.g., by CPU), they can jump around. Locking the relative positioning of the process, like HTOP does, would make it much easier to confidentially kill a process without worrying you might accidentally select something else.

[ClementTsang]

I've come across this myself, might look at adding a key that lets you toggle this behaviour or something.

For now I guess a workaround is searching for the process to ensure it is the only option; not great but at least it's safer.