After switching to Visual Studio Code as LaTeX editor, I installed the LaTeX Workshop extension to gain decent support for editing LaTeX files on Code.
After fiddling around with the settings, I still was not able to use Preview on macOS.
First of all, make sure external PDF viewers are enabled in the user settings.
"latex-workshop.view.pdf.viewer": "external"
Furthermore, set Preview es external viewer. The trick here is, don’t think about Preview as a viewer, actually, it is the open command.
Just set up the viewer as you would start preview on a terminal.
open -a preview mybook.pdf
This command used for user settings eventually ends in the following section.
"latex-workshop.view.pdf.external.command": { "command": "open", "args": [ "-a", "preview", "%PDF%" ] }
With these settings, Preview will spawn with the created PDF right out of Visual Studio Code.