Hi Rob,
You can accomplish this by changing the Authentication Mode from SAML to INTERNAL.
Add a user like normal, but set the authenication to INTERNAL. If you don't get a login screen, then it's possible that the URL you're using to login has a "tenantId" in it. For example, this URL snippet auto-logs us in with SSO:
.../desktop/index.html?tenantId=Infogix
but this one brings up the login page (if you aren't already authenicated):
.../desktop/index.html
Below is a screenshot for authentication type for creating a user: