Yeah, indeed there's not too much documentation in regards this, but be aware that this is currently experimental. It may be there in the next release as a fully exposed feature or will be removed. Not known yet. Please note this as well!
So, as you may already know these parameters officially are defined as follows:
Name Description Type Notes notification_id A string identifying feature_name.notification_name
A string identifying feature_name.notification_name to indicate a notification watcher is interested in receiving notifications for the URI identified by the feature_name.notification_name.
string uri_filters Optional list of URIs array of string
There might be a list for the "notification_id", but it is not currently exposed (I cannot find anything public yet).
Since notification feature is available for Service Insertion so I assume you work for a partner trying to utilize it. In that case it would be more advisable to engage through partner support channels to get the currently available list of parameters officially from our developers.
Having said that can you please elaborate a bit more on your request :
... my goal is to sync DFW group membership information from NSX-T...
What is the reason behind this? Cannot you sync from AD or LDAP directly? Maybe there are other ways to achieve what you want knowing the "big picture".
Note: even though I work for VMware the notes here are mine and must not be treated as an official response from VMware.