Hi Robert,
thanks for the the link to the other discussion. Alas, I was of course hoping for something out-of-the-box in terms of some kind of WAB configuration for applying permissions to a widget akin to applying permissions to a web map, but I suspected that was not likely something in place yet in WAB.
If I understand correctly, we will need to develop a "widget visibility control" widget that runs at startup and has the function of getting the username/group and then sets the visible state of each widget depending on which widgets are allowed for a particular user/group.