Self's environment was a panning desktop where you would inspect an object's slots and as you kept opening things, they would exist in some space nearby. You could, in theory, keep these things open and have a much more spatial feeling about the system.

I don't remember there being any way to collapse and re-expand this context so that it could persist yet be out of the way when you didn't want to look at it.

Talking about Self... https://github.com/pavel-krivanek/Selfie

...but the infinite desktop is still missing there.