Thanks for your question.
Unfortunately, it won’t be possible to change the tenant admin email address directly on the Dashboard.
As a workaround, you could try inviting your new tenant admin member, and then removing the old one on your Dashboard settings.
Please refer to our Transferring ownership of a tenant - #2 by rueben.tiow thread for more details.
If anything else comes up, please feel free to reach out to us again.
Cheers,
Rueben