For those of you with a Galaxy S4, Note 2, S3, Note 10.1, or Note 8.0, there’s an easy way to enable all apps for multi-window now using the Multi-Window Manager App. Before, the user had to install a custom ROM or a multi-window MOD to make this work but with the app, all you need is root.
The stock Samsung firmware only supports multi-window for few selected apps like stock browser and GMail. By using this app, you will easily enable all of your apps for full multi-window.
You will need root for this app so make sure your Samsung Android smartphone or tablet is already rooted before installing the app.
Once the app is installed, enabled all of your favorite apps for full multi-window is easy, simply enable it and reboot. Once rebooted, you will be able to use your selected apps in multi-window.