I have been working on improving how delivery lists are stored and managed as a Google Summer of Code student. Currently, I have completed the new backend, an interface for creating delivery lists (and importing from the current format), a basic interface for editing raw list content, an API for adding / removing target pages, and a list view that supports in-place removal and addition of pages. I will also create a UI for adding / removing multiple pages simultaneously and write tests for the features I've implemented. You can track my progress here. Please feel free to raise any questions or suggestions. Thanks.
Topic on Extension talk:MassMessage/Flow
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Ok, I'll take a look there.
Is there a public test wiki?
I just set one up at http://mm-ch.wmflabs.org/wiki/Test!.