What is the best way to handle multiple launch targets in SBT?

I am trying to create a Build.scala that has several projects / goals for a launch action. I started trying to define it as a subproject like:

val this_one = Project(
    id = "Main",
    base = file(".")
    settings = ...
)

First of all, I assume that I have the wrong settings, or the configuration is not included in the project definition like this.

To develop a bit, I have several core () that I want to run in the same source tree. There are several tools that come with the main project, and I would like to be able to selectively execute them from the sbt console.