I have one Lightroom Catalog with two top level folders. Both folders point to the same physical network storage location with the difference being that one folder uses the UNC path while the other uses a mapped drive. So it looks something like this in the Library Module:
Multimedia (\\192.168.1.3) (M:) 1297 Photos \\192.168.1.3\Multimedia 17135 Photos
This happened because I imported using a mapped drive instead of the UNC path.
I want the mapped drive content to be located under the UNC folder so everything is under the same top level folder. Also, because I didn't notice the issue at first I made adjustments to some of the mapped drive photos and (ideally) I don't want to lose any adjustments that were made.