SplitView divides the current editor pane into two separate panes, showing the same script.
With SplitView, you can navigate to two different spots in your script at the same time, and work on two different areas of your script. This is useful in larger scripts where you would like to keep an eye on one spot while working on another.
To enable SplitView for a particular editor pane, identify the SplitView thumb at the top of the vertical scrollbar, and drag it downwards.
This will split the view, and you can adjust the height anytime by dragging the separator bar between the two views.
There is no way to disable a SplitView once it is created, but you can always drag the separator bar all the way to the top to hide the top view.
Top and Bottom View
The bottom view is always the original editor view. The top view is added by ISESteroids. It is a fully functional editor, and you can edit your script document in both views.
There are certain limitations that apply to the top view, though. For example, breakpoints are displayed a little differently in the top view, and there may not always be all features available in the top view.
So if you encounter limitations in the top view, simply switch to the bottom view, and perform your edits in the original editor instead.