I have made contact with
palbogil who has had a look at where we are on this matter. He thinks that the drop-down menu is probably hard-coded and therefore modifications will be very difficult. As a consequence we seem to have reached a dead end. It's a shame, having come so close to a solution and my thanks go once again to all those who have contributed.
I have given up on modifying a template and installed
Word size of FreeCAD: 64-bit
Version: 0.19.24291 (Git)
Build type: Release
Branch: releases/FreeCAD-0-19
I have been able to define a GUI with softer, glare-free colours yet with the sort of definition I was seeking for taking screen videos.
FTR: contacting
palbogil had nothing to do with a pinging process. I didn't know a ping would carry a message to someone - that's why I was mystified. Generally speaking a ping command sends packets of data to a specific IP address and then returns data transmission and response time. Its used to check connections on a network. It doesn't carry text. That's as I understand it, anyway.
However, I stand to be corrected if I am in error.
BTW: if I appear obtuse read that I am confused.