"Enter" parameter

The System.Environment.NewLine is for business rules of course, but you didn't say that this was something that you needed for CubeViews.
Where are you attempting to put multi-line text? Is it in a column header, row header, or in the data cells as part of a V#Annotation (cell detail) view?   The Data Explorer view will not show multi-line text reliably on row/column headers (may have cropping issues) : you can use an XFBR expression to run an XFBR rule to return a multi-line string; just no guarantee how it will look in the Data Explorer view.  This is how mine looks:
Row definition:  A#16000:Name(XFBR(CubeViewLists,GetMultiLineText))

Cell detail text (such as V#Anotation view) Also won't display multi-line text in the Data Explorer view.
Even if you have a DynamicCalc that returns a successful multi-line string, the CubeView will show the text on one line.

For Report View output, the same limitation applies I believe ( it still displays multi-line text on a single line )