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Right now managing platforms is really limited to adding them. I suggest having more support like installing/uninstalling plugins (for custom platforms it should be forced to be on a shared folder). Also upgrading the custom libraries is a manual task (right now I handle that with ant copying stuff from the Default Platform).
harness/README gives instructions how to manage platforms manually.
I'm aware, I'm requesting IDE support for that.
Doubtful that there will ever be resources to implement something like this, especially since the things you discuss essentially come for free with Maven.