Not sure why this feature is hidden so well-- its always been that way.

In the repository under the "Contexts" tree, find you DB context. if you havnt made one yet-- by pressing "export to context" in the DB connection wizard-- make one.

Right click the context and select "edit context groups"
click Next to go to "Step 2 of 2"
click "Values as table"
in the far right of the window there will be a little button hidden near the top of the "Values as table" tab. click it.
In the Configure contexts window click "New" give the new group a name (i.e. "test") keep adding groups till you have all your environments defined.

Once you've added the groups you can define which group will be applied to a run of the job by selecting it from the Run dialog or by feeding the name to the exported scripts from the command line (--context=test)