I asked this question toward the end of last summer and I believe the answer is no. I think snapshot is kin to "Record" on an LX desk, capturing the entire output (or single layer) and "record"ing it to a preset. I do not believe there is an equivalent to "Update" on an LX desk, which is what you are looking for. Some command that only grabs things that have been touched. I think this is where Catalyst stops and says, "If you want LX desk control features, then use an LX desk". Fair point, but not useful for those struggling with standalone systems.

Kevin