Hi all,
It's hard to convice you guys, but I hope now it will become clear to all. Now I can give you the correct query:
These pinned folders are saved in the index.dat file. In this Index-file there are as well the other recent saved documents. This file is save under:
C:\Users\User\AppData\Roaming\Microsoft\Office\Recent\index.dat
I see no possibilities to exclude something inside the index.dat file. This is the reason why I exclude "Office 2013" from my clean. "Office 2013" deletes this file.