@NFSCoder-9821 Thanks for reaching out. We don't have a Rest Api call to fetch the users based on created by parameter. I believe this information is not logged as the users can be either created from the portal or the users will be added automatically under users blade when they try to signup in the developer portal.
You can also leave your feedback on our APIM feedback page https://aka.ms/apimwish so that other users who are in need to similar feature can upvote it and PG can take it forward.
please let me know incase of further queries, I would be happy to assist you.
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