(not able to edit/disable a FsDreamTeam scenery in the library)
This is entirely normal, as explained in so many other threads, you disable a scenery addon with the Options->Add-ons menu.
In Add-ons menu of P3D v4, I doesn't have each FsDeamTeam scenery.
This is not normal. If you see the sceneries greyed out in the Scenery Library, as in your screenshot, it means they have been added as "Add-ons", otherwise they wouldn't be there listed in that way so, it's just not possible they wouldn't be visible in the Options->Add-ons menu.