how to autohide the panel?

[hw <hw@xxxxxxxxxxxx>]

Hi,

I have set the panel to autohide and it's not hiding except
sometimes :(  Instead the windows go underneath the panel,
which is very annoying.

Is there a way to get the panel to automatically hide like it's
supposed to?  How is it possible that even simple things like
this still aren't working after 25 years or so of KDE?