For future updates, I've created a go-folder to make preserving and updating my whitelists easy.
1. Create a folder on your desktop (or other easily accessible location) called, e.g., "Dorico VST."
2. Go to the folder where defaults.xml is located, and create a shortcut/alias. Place it in the new folder.
3. Copy (do not alias) your defaults.xml file into the new folder as well.
4. Repeat steps 2-3 for the VST whitelist file.
5. Done! Now, when Dorico updates, you can restore your whitelists by copying the files into the aliases of their proper folders. This also makes it easier to update those files for new VSTs.
Dorico 1.0.30, MacOS 10.12.4
I dive into new/beta versions like birds dive into plate glass.