Unlocking 60 to 75 is now possible at the service center. Part number:
BATTERY UPGRADE, 60kWh to 75 kWh, MS(1091845-06-A)
Cost now is $2250 plus $10 labor for the new 75 badge plus tax.
They also think that the option to upgrade is available in the app under upgrades, but it wasn't for me.
After almost 4 years of ownership, I wanted to get the additional range to cover the 13 miles that I've gradually lost.