The Graph widget does not allow you to select freely which data sets you want in front. For data sets of the same type it works as expected: a data set further down the list is drawn later and over other data sets. 

However, data sets with Stacked Lines are ALWAYS drawn over simple Lines and Points are ALWAYS drawn over Lines and Stacked Lines.

This is particularly annoying when displaying a stacked graph together with a regular one.

 

See attached example.