Hi Timmy,
The answer is simple. You can make an addon scenery folder anywhere you want. Mine is on my "M:" drive, while my sim is on the "P:" drive. My directory looks like ...
M:\Lockheed Martin P3Dv3
- \addon scenery
- - \Return to Misty Moorings
- - - - \(first RTMM scenery folder)
- - - - - - \scenery
- - - - - - \texture
- - - - \(next RTMM scenery folder)
- - - - - - \scenery
- - - - - - \texture
Just navigate to your new directory location when adding scenery to your sim's scenery library.
When I migrated to the new P3D, I just copied my entire addon scenery folder from where it was, into the M: drive (inside a "Lockheed Martin P3Dv3" folder so I could find it later). Then I rebuilt my new scenery library from the bottom up, using that new location.