How to upgrade an existing account to CE via product key?

[hqdm]

I can't figure out where to go on the Mogstation to enter my product key.

There's the obvious page to upgrade through the SQEX storefront for $20, but that's not what I'm looking for. It's a full vers code for the CE that I want to apply to my current Standard version for the item bonuses, foregoing the 30 days.

All the support faqs just direct me to the $20 payment page, which I have no use for.

e: welp, apparently you can't according to chat support.