VST Sound - Move to external HDD

Best way to do it would be to use the installer and choose the desired location for the content. By default it goes to AppData/Steinberg/…
If you change it from default it will create shortcuts in the default location pointing to wherever you installed the content.
It can be a different drive.

You can also check this thread: Installing HALion 5 across two drives - Virtual instruments - Steinberg Forums