Yes, I'm replying to my own question... :-)
I figured it out. There's a cotter pin holding the tether in place. But that cotter pin also holds the mechanism for the Honda's gas cap to be turned off for transport and on for using the generator. Since I may run a single generator from time to time, I need to keep the OEM gas caps. So - I removed the cotter pin, picked up all the spring loaded parts off the floor :groan: reassembled with the cotter pin holding in the mechanism and put the top if the tether in the neck of the fill area. Hopefully the pics explain it.
Tethered cap - cotter pin in center
Tether removed, mechanism restacked
Top of tether
Top of tether placed inside fill area
BERG cap installed