a
There's no such thing as a "local group" in SolarWinds. If you want groups, you have to use AD. There are local (ie: solarwinds only) user accounts, but not groups.
That being said, nothing is stopping you from creating a completely separate AD server with it's own closed domain with a trust to the "real" domain, setting up groups there, adding your user accounts into those groups, and having Solarwinds authenticate against that domain for user permissions. It's a little round-about, but it would get you what you seem to be describing.
