Hello Michael,
By "Manually editing device records" I assume you mean making changes at the contract level. This functionality is not currently available in the portal. Any changes need to be submitted to the Cisco Support team. This can be done through your partner (Cisco reseller), your Cisco Account team, or directly with customer support by opening a case in My Cisco Workspace. You can leverage the information obtained from the portal for this purpose (serial number, contract number, site information, etc.).
You can find the details on how to do this in the Support section of the Useful Links page in the portal.
Thanks,
Nathalie