Like Sonar, Cubase uses instrument definitions, called "patchnames" for use with your hardware synth. They are standard TXT files and are found in the
C:\Users\yourname\AppData\Roaming\Steinberg\Cubase\Scripts\patchnames folder. Any files you create must go in the
Inactive folder to work.
C:\Program Folders\Steinberg\Cubase\Scripts\patchnames seems to be a dummy folder as nothing I put there shows up in Cubase.
You can write your own files or here's a
utility that can convert Sonar .ins files to Cubase formatted .txt files. Tho it may not work for some hardware it worked for me. From there just follow the instructions
here to set them up in Cubase.
My synth has 10 banks of 10 voices each arranged in random order. This utility rearranges them by instrument. If you'd rather have the patchnames in the same order as they are in your synth you'll have to do some cutting and pasting after the file is created.