Whitelisting became much easier in Dorico 2. Go to the Dorico preferences dialog, choose the Play tab and scroll all the way down. There are two buttons, ‘Edit VST2 Whitelist’ and ‘VST2 Plug-in Paths’.
Editor windows will open where you simply add the plug-in’s name that you want to whitelist or add the path to the path list, if it is somewhere located outside the standard paths.