The idea of the Sublime Text plugin is that you enter Scala REPL commands into a file, then hit a keystroke to send the commands to the REPL. The plugin will display the results in another editor view and align them with the input so you can easily see which result was produced by which command. It’s a nice way to try some things out without having to re-enter or edit things in the REPL itself.
The project page has more details. Please let me know how it goes if you try it out.