Hello Mark,
MV> Ah ... I didn't see that link before. MV> I haven't run across .pr files yet. What opens those?
well, a project. You can think of a project like a switchable Linux Desktop. World Menu, Open, Morphic Project opens a new one.
They can be nested, jumped to and deleted. And saved to .pr files.
So if you load your pluggableDemo.pr your desktop will be replaced by that project. You get back via World Menu, previous project.
Each project carries its own changeset which gets the current cs when you enter that (never used cs myself).
I use Squeak Projects to work on different aspects of my Software projects.
For example in one Project I have Browsers, Workspaces, Inspectors of my model classes while in another Project I might have Browsers on my database connection classes.
Switching projects is faster than opening or expanding Browser Windows.