I ended up manually copying the .prefPane file to:
/Library/PreferencePanes
After restarting Settings.app, it finally appeared on the list and worked perfectly.
As Martijn Scheffer stated in this comment, the reason for the pane not appearing in System Preferences is that the installer incorrectly puts the file to ~/Library/PreferencePanes instead of /Library/PreferencePanes.
Download in https://developer.apple.com/download/more/ Additional Tools for Xcode 10.1

