Hello from the future. For anyone still looking for an answer to this question: the property in settings was hidden at some point. However, since it’s still part of the API, you can still configure it using the Command bar. Paste this in to see it go poof:
settings().Studio["Show CorePackages"] = false
To bring it back, you’ll need to run the same code again but with true instead.
Disclaimer: I’m not guaranteeing this property will still exist or function in the future, nor am I responsible if you break something when you fiddle with the guts of Studio.