Am Sonntag 18 Dezember 2016 schrieb Leslie Turriff:
> 	Okay, I tried this, but it's not working for me.  Here's what I did and
> what happened:
>
> 1)	I renamed ~/.trinity/share/apps/kate to ~/.trinity/share/apps/kate~
> 2)	I started kate (using its icon), then closed it.
> 	kate created a new apps directory, with an empty sessions subdirectory.
In my case it created also the file "default.session" in sessions subdirectory, 
which I could then edit as demonstrated. But it is not necessary, see below... 

> 3)	I restarted kate and it still shows the sidebar with the file names.
> 4)	I tried creating and saving a dummy file to make kate create a session,
> but its sessions subdirectory remains empty. :-(
>
> On 2016-12-17 09:16:20 Stefan Krusche wrote:
> > After a little experimenting I found this workaround:
> >
> > 1) Start with pristine kate config dir
> >
> > cp ~/.trinity/share/apps/kate{,orig}
> >
> > 2) Open kate with no arguments and close it
> >
> > 3) Open ~/.trinity/share/apps/kate/sessions/default.session with an
> > editor and change these options to "false" and save file.
> > Kate-MDI-Sidebar-Visible=false
> > Kate-MDI-ToolView-kate_filelist-Visible=false
> >
> > 4) Next time you open kate it will neither show the side bar nor the
> > document list.
>

Maybe you have not noticed yet, but there is a new mail which point out a much 
more convenient way to achieve what you wanted:

> Am Sonntag 18 Dezember 2016 schrieb Michele Calgaro:
> Kate -> Settings -> Configure Kate -> Session: provides option for session
> management when opening and closing Kate. In particular if you choose
> "Manually choose session" you will be presented with a dialog where to select
> the session to use when you start Kate

After you close kate and start it again with no arguments a dialog will pop up 
and ask for which session to open. In that dialog you can choose your preferred 
session and click the button for keeping it permanently as your default 
session. When you have done that, the dialog will not pop up again when you 
start up kate next time, but your chosen default session will be opened.

regards!
Stefan