Multiline is not supported by sass. Reading the doc, there is one exception, when it comes to multiple css selectors like in this example:
.users #userTab,
.posts #postTab
width: 100px
height: 30px
Read the doc here: http://sass-lang.com/docs/yardoc/file.INDENTED_SYNTAX.html#multiline_selectors
So, sadly: There is no possibility to get multi-line support for an argument list in sass.