Powerpoint on 3 Screens with Presenter View NOT on the Built in LCD
I'm posting a solution to a problem that had me at my breaking point. You have 2 external displays connected to your Mac. You want to run PowerPoint and present your slides on one external display, and then have your Presenter Notes display on the 2nd external display (not your built in LCD display). In PowerPoint on the Mac, the notes will always default to display on your Primary Display.
The solution is to control which display the Mac considers the Primary Display. In System Preferences, under the display options, click on the tab that will show you the Arrangement controls. If you are seeing 3 displays, you can hold down the option key, then click and drag the built in LCD over top of the display you want your slides to display on for your audience. This will mirror the LCD with that display. Next you want to carefully click on the top white banner for the LCD and drag it to the 2nd display that you want your Presenter Notes to appear on. When finished, you want the window to look like the screenshot below.
Now, when you start the slide show, your Slides should display for the audience and on the Built in LCD and your notes should display on the 2nd Display you intend to be viewable for the presenter.