Seems to me that Combinatorialism is a missing subcategory of Possible Worlds that would usefully include not only Armstrong's important work and the scores of papers it has inspired but also related papers by and about Quine, Cresswell, and others.  It also strikes me that Actualism is a natural subcategory to include under Theories of Modality alongside Modal Realism and Modal Primitivism.

I really appreciate this tremendous resource and the thought and effort that have gone into it.

-chris