[Radiant] default content of body and page parts tabs

[Hadi S.]

Hi,

i am new to Radiant and trying to find out how to set the default
content for the body and page parts tabs. Is there a way or any
extensions available to do that in Radiant?
On the admin backend under Settings/Application there is the
possibility to set the deafult page parts. But i can't see any way of
setting the default content of this parts.