Smart Locks Home Solution? Did miss something?

Yep, one of the minor quirks of the stock DTH. I think at some point in future they may add support to change the digits remotely but for now it’s better to program the digits before pairing the lock when using the stock DTH.

If you’re using the Enhanced Z-Wave lock DTH, which also works with SmartLocks, you can tap the refresh button and it’ll update all the lock parameters including the code length.