I was disappointed to find Android only natively supports one full screen window at a time. The Nexus 10 can handle multitasking yet Google has stubbornly refused to add it. Some Samsung devices and the Paranoid ROM (recently dropped apparently) feature their own implementations of multi-window support as well as some builds of OmniROM (but not the Nexus 10 builds). Luckily a few developers have created Xposed modules that allow for running multiple windows at once for any ROM or Android device. Unfortunately, it’s not a very straightforward process but after a bit of tinkering I was able to get it up and running. Root is required to install the Xposed framework but this will work on any ROM including stock. If you need to root I recommend the Nexus Root Toolkit, which will do it safely with a few clicks.

Setup multi-window mode in Android: