You would need to query the NodesSettings table to show which CredentialID is being used, and correlate that with the Credentials table. I’m not in front of my PC at the moment but will see if I can get a query together later if you still need it.
SELECT Credential.Name, nodes.Caption, nodes.NodeID,
ON nodes.NodeID = Nodesettings.NodeID
ON nodesettings.SettingValue = Credential.ID
WHERE nodes.ObjectSubType = 'WMI'
AND nodesettings.SettingName = 'WMICredential'
ORDER BY Credential.Name, nodes.Caption, nodesettings.SettingValue
Check out aLTeReGo's report, as this is probably what you are after.
Oh this might be helpful to see the usernames from the credentials groups above:
/****** WMI Credentials - Group and usernames ******/
SELECT c.ID ,c.Name ,cp.Value
-- ,c.CredentialType ,c.CredentialOwner ,cp.Name
FROM Credential c
INNER JOIN CredentialProperty cp ON c.ID = cp.CredentialID
WHERE c.CredentialOwner LIKE 'Orion'
AND c.CredentialType LIKE 'SolarWinds.Orion.Core.SharedCredentials.Credentials.UsernamePasswordCredential'
AND cp.Name LIKE 'Username'