I don't actually use Nitrous. But here are some steps that you may find useful.
1) Write a random text with multiple lines in Nitrous.
2) Open that file in Notepad++.
3) Goto "View --> Show Symbol --> Show End of Line".
4) Find what symbol it uses as new line. You can find more about this Here.
5) Now while writing any text that you wish to open in Nitrous, in place of Enter (Notepad uses symbol "LF") just place that symbol.
This is not very intelligent method, I accept. But this would do the job.