Reg Key "AUC_REGK_EXPORT_WIN2PDF_DRIVER"

Problem:
Smart PDF Export has to be in grayscale.
If I export using "Colors to black" the layout diagram of the IEC samle projekt outputs unreadable. (see attachment)
If I use some PDF printer to convert my Smart PDF to a grayscale PDF I loos the navigation.

Possible solution
In the EBDN I found this registry key

 AUC_REGK_EXPORT_WIN2PDF_DRIVER

So my idea is to use another pdf print driver that can convert colors to grayscale and replace the driver to use using this reg key.

But how to use this reg key. Documentation only says that I can not use the pdf drivers name.
So what "name" to use instead?
How to get or find this "name"?
And is the driver set by this key used by Smart PDF too?

Thanks a lot and kindly regards from Vienna,
Harald