I'd say it's probably simplest to just do "Resolved Document" -> "For
Styling" from the Edit menu. The process to build it uses the composition
pipeline with a fair number of steps along the way, so I don't think
there'd be much bang for the buck in trying to recreate the function
outside of Editor. You might be able to find a copy in .aptcache, but that
would only be as up-to-date as the last publishing operation.
I've noticed on at least one project, where I was using this function
fairly often, that Editor (6.0, anyway) seems to leave a copy of the
generated RDS on disk next to the DITA map, gradually accumulating quite a
collection of sequentially-numbered versions.
-Brandon 🙂