OK. Just called Samsung support and found a solution that did not require resetting the hub and reconfiguring my 100+ devices.
There is a way to change the ID (email address) of the Samsung account.
At account.samsung.com, you sign in to your current Samsung account, click on your current ID/email, and it will offer the option of changing to a new ID/email.
The key is that the new ID (which unfortunately must be an email address) must not already be associated with an existing Samsung account. Upon making the change, it asks for a password (use the current password of the current Samsung account). It will then automatically create a new Samsung account with the new ID/email and the same old password (which you can always change later).
You then logout of the apps and log back in with the new Samsung account credentials. All hub setup/configuration is retained.
I took the advice of an earlier post and created a new gmail account using the physical house address. That is now the ID/email associated with the hub and the new Samsung account.
Now I can freely tweak the configuration to get it ready for the new owners (without disturbing them at their actual email address). I will simply give them this new gmail account and they will be up and running.