It's good to know those options and techniques. Thanks for suggesting.
I've determined that even if I do create a work around, this is undesired functionality. The filter needs to be visible only to user/browser that is setting the filter.
When these restricted users use the Filter option in a sheet that they cannot edit, they can create these 'Temporary Filters'; and that is the functionality I need to chase down.
In their browser window, Sheets will apply a black horizontal and vertical bars, then allow you to select a filter for each column, just like it normally does. It can be saved, and it's visible only to that user session.
Brilliant.
I want to call that in GAS.