It is not quit clear to me what you try to achieve.
Do you want to use an other library for your schematics. Just change the path to the library in the settings and you are done. Packaging errors
But do you want to merge the two libraries into one new library. Open the library in the library manager, export everything in the EDX
format (file->export EDX), select everything you want to export and hit the button.
You can import the generated EDX file into a new or existing library. (File->Import EDX)
The core of the problem is that we maintain internal part numbers in our DB but our sister BU did not. How do we map these attributes onto the symbols in their design?
I forgot to mention previously that we both use Netlist flow.