Onyx International BOOX Nova2 User Manual page 123

The Apps Split-Screen defaults to landscape mode. The left side
defaults to the main application and the newly opened application is on
the right side. You can swap left and right positions in the Split-Screen
Menu;
Under Split-Screen mode, select Exit Split-Screen to exit the
Split-screen mode from the system pull-down Split-Screen menu.
After exiting the Split-Screen, the interface will return to the main
application on the left by default;