No credit to me. I found this on Tesla Motors Club:
Basically, what you can do is have Maps at the top 1/4 of the screen, a small Media window at the upper-middle part of the screen, and whichever app you want at the bottom half of the screen. Here's how:
1) Open the app you want to have on the bottom
2) Then touch the Media (music) app button so that that pops up
3) Put one finger on the top of the Media app part of the screen and another finger on the App launcher icon. Then, while holding both fingers on the screen, drag up. You will move the Media app window up and also open that last app you'd opened (the one in #1 above).
Voila! Now you can have Maps + Media + another app (could be camera, browser, energy, calendar, or phone) open simultaneously.