Hi Bob @apella12 Thanks!
It turns out Zooz sent me the (standalone) “PC Controller” package by e-mail right before lunch. I ran that completely independently of Simplicity Studio and while the PC Controller software is able to run, it was not able to update the firmware as I got blocked at step 6 of Zooz’s firmware update instructions – the device can not get “added” in they way they suggest.
See attached screenshot
After lunch I removed, reset, etc. everything I could between the slaves and the controller (let’s hope that doesn’t turn out to have been a bad decision! 
)
Now I seem to be able to do even less with the provided “PC Controller” software (including “re”-adding the Zooz stick)
I am again waiting on hearing from the company for advice on bending their controller to my will.
BTW: yes, I was logged in to Simplicity Studio, but I had the stick plugged in. Perhaps that is why I did not see the package manager (I had only device and product group options).
BTW#2: your Simplicity Studio looks quite different than mine. Looks like you are running on Linux (I am/was on Win 10 in a VM as they – Zooz et al – seem to prefer that. Only Ubuntu is “supported” in Linux and I am mostly working on new Fedora installs here. I don’t want them to claim it is not working because of platform issues.