The Nitrous.io IDE appears to have 4 parts. There's a file browser, a text editor, a console/terminal, and a chat window. It appears that the only way to open a file in the text editor is from the file browser. This only allows me to open files within my home directory. Is there any way to open files in the text editor from the console?
You cannot open a file from the shell into the web interface because the web interface is not linked to the shell. The shell is a SSH terminal, which means you can alternately terminal editors such as vi, vim, nano, or emacs.