The curator guide doesn’t specify but if it a taxa with multiple subspecies, even after, is split, which output taxa are the subspecies transferred to?
Wouldn’t you have to go to the publication that did the taxonomic revision to see what they did with the subspecies, assuming they retained them or bothered to address them?
I would think this is the case. Otherwise, it’d make sense to assume that they are synonymized, because how else would they be split between two new species if not specified.
In some cases they might give distributions for the two species and that might solve the subspecies issues fully or at least partially.
Nowadays many subspecies are either elevated to species level or they get “sunk”. Not all of course but that’s a trend in many taxonomic groups.
If you’re asking about what the system would do with the IDs, it would depend on whether the input taxon was also an output taxon. If so, I wouldn’t think anything would happen to the subspecies IDs. If not, I would think the split wouldn’t go because there would be active children of an inactive parent. But I don’t know for sure; sometimes unexpected things happen, especially with subspecies.
As for advice, I would echo previous posts in suggesting subspecies be addressed (e.g. with swaps) before the split.