The latest SkywarnPlus version is v0.8.1 which was released 6 months ago. If you already have this version, then updating will do nothing for you.
No version of SkywarnPlus beyond the initial release contained any changes to the list of “possible” alerts, so even if you are using an old version, it will make no difference.
The NWS API specification is not accurate and needs to be updated. Until that happens, there is no way for developers such as myself to include support for alerts that technically do not exist.