Have you seen the MacPad by Federico Viticci of MacStories.net? He achieves it with zero actual hacks, and only 1 custom Shortcut. It lets the iPad be an iPad by default, but also act as a Mac display at the press of a shortcut. As long as your files are in iCloud, it appears to furnishes forth a seamless experience. https://www.macstories.net/stories/macpad-how-i-created-the-...