Within the project (or region) you can filter by taxa, so searching only for mammals or only for a specific genus is easy to do.
Values like native, endangered, etc generally have to be user assigned, so not all species that fall into this are listed as such. That said, you can also filter results for some of these basic characteristics, and there are more detailed and complex searches that can be done by editing the URL.
Here’s a page for showing how to do the latter:
When it comes to detailed lists of what’s native or not the best resource is going to be a site that’s Korea specific, probably part of the environmental branch of the government will have the best info.
There’s also this 800 page book Nam, et al., 2018 Inventory and Management of Endemic species of Korea from the National Institute of Biodiversity Resources. Here’s a PDF copy of it.
And the main site