The keyboard can be hidden by placing SaurusHideKeys.cfg in plugin directory.
On PC:
Place any file called SaurusHideKeys.cfg in the same directory as the Saurus.dll
This is mostly C:\Program Files\Steinberg\VstPlugins\
On Mac:
Place any file called SaurusHideKeys.cfg to Library/Audio/Plug-Ins/
Then restart Saurus.
If you delete the file the keyboard will reappear again.