[AQUOS] How to use split screen to display two apps at the same time

The split screen feature allows you to open two apps that support it at the same time, one on top of the other (or the other side of the screen).
If you try to open an app that does not support it, a warning will be displayed.
However, there is a way to force these apps into split screen, so we will explain how to use split screen, including that.