This thread was an eye opener.
I don't want to high jack it so here I go. I took the time to study Jeremy Brown's proposed solution. Very enlightening. First, I find the "Web Address" builder very inspiring. A clean way to build and troubleshoot an advanced Web Viewer URL/widget. Not sure if this is common practice or Jeremy's own way to do it but kudos for the inspiration.
And second, this simple three lines script first completely eluded me:
Close popover Go to Record/Request/Page [With dialog:Off; $rec] Exit Script [Text Result:""]
But... but... the local $rec variable was never defined???
The answer was in the JSFunction:
var theURL = "fmp://$/**FileName**?script=Nav_GoToRecord&$rec="+value; window.location = theURL;
Wow, we can launch a script from the Web Viewer, and define a variable outside of this script?!?!?! This is so powerful, I want to learn more!
Thank you for your time, and especially you Jeremy this time.