In short, these libraries are all located in *.vstsound files. Where it gets tricky is you can ONLY move the library files but not .vstsound files associated with the core program(s). I think I avoided moving and of those files which don’t appear to be actual sound libraries (eg not Cubase files).
Next open media bay (F5) and make sure the new directory is checked and then do a quick scan (via right click) to activate that location. If Cubase finds any of the sounds missing you it should ask you to point to the new location and that should be all that’s needed.