Preferences.sublime-settings

// ~/Library/Application\ Support/Sublime\ Text\ 3/Packages/User

// Settings in here override those in "Default/Preferences.sublime-settings",
// and are overridden in turn by syntax-specific settings.
{
    // Mac only: When files are opened from finder, or by dragging onto the
    // dock icon, this controls if a new window is created or not.
    "open_files_in_new_window": false,
}