Thank you, Dean, for your suggestions - and the screenshots, of course.
When overthinking it soberly, I've needed Orbx Central 'only' for installation, eventual updates or the detection of new products.
The latter two , I fear, won't come true for P3Dv6.
And the installation is - hopefully - a once and forever - procedure.
I've got all sceneries installed within the P3Dv5 folder, except for those, which required the external library.
So I'm thinking about cheating to Orbx Central:
At the moment a mere theoretical plan: Rename all paths from "Prepar3D v5" to "Prepar3D v5.old", then rename all paths from "Prepar3D v6" to "Prepar3D v5".
Then run Orbx Central to "re-install" the sceneries (most probably into a library folder!).
When finished, rename back all folders before running P3D again - and ... (I hope!) voilá!
Has anyone already tried this way?
Michael