usually on installing VST plugins there is the choice to put VST2 plugs to any folder of your liking (as long as the location is included in the cubase VST path.)
but for VST3 plugins there is only the Common Files/VST3 location and no choice to select other locations.
can i somehow point cubase to a VST3 folder of my choice?
no. VST3 plugins are meant to be installed in …/common files/VST3 (on windows)
Correct. However, if you find it of use, within this folder you can create subfolders. I create them by manufacturer, for example.
Under Windows, only by using a junction point to store the actual plugins elsewhere, while programs like Cubase think they are still where they ‘should’ be.