Workflow Status Details including user names

I'm looking to add user names to the workflow status report we've already created but I can't seem to find where in the database tables that info is tracked. We've manipulated the WorkflowStatus method query to pull in the WF steps and the status of each. For example: 

I reached out to OS support and they pointed me to these two posts, one of which mentions CertifySignOffInstances. 
Workflow Confirm and Certify Users Info | OneStream Community
Displaying user names on the workflow status report | OneStream Community

I can also see WorkflowLockHistory as a table but any thoughts on which other tables store workflow status by user info? Appreciate any direction you're able to provide! 

Thanks!