Hi Stefan,
I would say that what you request is non-standard behavior.
It is designed to appear on mouse hover, like this is done in all other apps 
Upps

i didn't think on such.
Do you know some example application where it is done with mouse click only?
No, and i didn't check this. It was just an idea.
And maybe we can check why it disturbs you? 
It's just the panel suddenly appears if i take the mouse over the hidden pane button.
I mean even if i didn't want open the panes,... it's just my hand which goes that way
without my permission

It's just to not let the pane get open every time you go to the left with the mouse.
So an opening delay would work for that issue too.
I just tried <HoveringDelay>6000</HoveringDelay> without success

Maybe smtg like
<HiddenPaneOpenDelay>4000<HiddenPaneOpenDelay>
and
<HiddenPaneCloseDelay>1000</HiddenPaneCloseDelay>
is doable?
But only if some free time.